I love the Caymans and have lots of suggestions!
First you should decide which Cayman Island that you would like to visit, below is the link to an article I posted on Trip Advisor regarding the differences (for a diver) between the 3 Cayman Islands that you may find of interest.
IMO, the best diving is available off of Little Cayman, followed by Cayman Brac, and then Grand Cayman - but there is excellent diving off of all 3 islands and they each have their unique characteristics and charm.
You can usually find a lot of flight options to get to GC but you will have to book a connecting flight on Cayman Air to get to one of the sister islands (LC or CB) - usually about an extra $100 roundtrip.
On the sister islands of LC and CB we prefer an all-inclusive resort with meals and diving included. That's because there is not a whole lot to do besides eat, sleep, and dive on the sister islands and the supply barge only stops once per week so there may not be much available in the small grocery stores.
On GC we prefer to rent a condo or apartment. There are lots of great restaurants and well-supplied supermarkets. We often cook simple breakfast and lunch meals and go out for dinner because eating out 3 times a day would be very expensive. There's lots of great night life on GC but not much on the sister islands.
On LC, we like to stay at the Little Cayman Beach Resort; you get to dive Bloody Bay Wall and Jackson's Bight and they are among the best dive sites in the Caribbean IMO. LCBR is a nice, clean, small, diver-dedicated resort with an excellent onsite, valet, dive operation (Reef Divers). The food is buffet style but very good. They have a small (but very good) SPA and an exercise room. The resort offers some free entertainment activities - Trivia Night is very popular - but the Scientists from the LC Marine Institute always win the free bottle of wine! (Oh well, they will surely enjoy it!)
There are other resorts on LC that also have onsite dive ops like Southern Cross but I have not tried them. We have only visited one off-campus restaurant (The Hungry Iquana) but it was really good. The lionfish tacos and cracked conch were both very tasty!
There's not a lot to do besides dive on LC. You can kayak, hike, bicycle and enjoy the wildlife preserves. I understand that there are some shore dives available from LC but I haven't tried them. Little Cayman is very popular because of the excellent diving, so it can get pricey and it books up fast. Even if you can find hotel accommodations you may have trouble getting flights to and from the island - so don't wait too long to book. There's not much night life on LC!
On CB we like to stay at the Cayman Brac Beach Resort (formerly the Brac Reef Beach Resort) this is a sister property to the LCBR and it has the same, excellent onsite, valet dive operation (Reef Divers). The diving around CB is really great but not the spectacular vistas of LC's Bloody Bay Wall. Again the resort is small and diver-dedicated and super nice. In fact, they have just completed a major renovation and now have a huge freeform infinity pool and a multi-level beach bar. It also has a small but nice Spa and an exercise room. The resort also offers guest activities and you would be amazed at the popularity of Bingo Night (the entire island joins in, guest, staff and locals!) And they have a great outdoor barbecue on Friday nights.
The food at CBBR is buffet style but very good - in fact I think it is better than LCBR. CB is a small, quiet island but there is a little more to do topside than on LC. Hiking, bicycling caving, climbing, nature preserves, and a few local restaurants and taverns. I am told that there is great snorkeling and shore diving off of CB but I haven't tried it. Again, there is not much night life on CB!
There is a nice, easy wreck dive available off of CB - a sunken Russian Frigate - and the resort will also take excursions over to Little Cayman for an extra fee (if the weather permits) and if enough guests are interested in diving BBW. (LCBR does the same thing and will take guests to dive the Russian Frigate off of CB.)
I don't know of any other hotels on CB but if you find a rental property I am told that Scuba Shack is a great dive op. CB is less popular than LC so it is usually a little cheaper and easier to book. You can also take a jet to CB from GC but the only way to get to LC is on small Otter airplanes. The flights are short whatever you book but the "wait to fly" rules do apply.
Grand Cayman is a whole different experience! It is the largest and most popular Cayman island and it has lots of shopping, gourmet restaurants, night life, attractions, and the powdery white sands and turquoise waters of the Seven Mile Beach which is a major draw for lots of tourists. There is very good diving around GC, the North Wall is fantastic and the East End has some great dive sites. The Kittiwake off of West Bay is a sunken US sub-tender and an easy and interesting wreck dive.
Diving isn't the main attraction on GC like it is on LC and CB - but there is still a lot of great diving and dive ops available. Try to avoid going with a dive op that caters to the cruise ship crowd.
Out on the East End the Compass Point Condos have the Ocean Frontiers dive op on site and they are a very popular operation. But you will be far away (at least a 45 minute drive) from the more popular attractions of GC and the diving can sometimes get rough on the East End.
Sunset House is on the South Sound just below 7MB and they offer an onsite dive op, shore diving on the house reef, and snorkeling. They are a hotel and not a condo but I think that they offer a meal plan. Cathy Church's photo studio and store are on-site. We have visited but never stayed there.
North of the 7MB you will find Cobalt Coast Grand Cayman Resort. This is a small, diver-dedicated resort that was recently purchased by the same company that owns LCBR and CBBR and they now have the same dive operation on site (Reef Divers). They offer an all-inclusive, buffet meal plan but they have some cottages with kitchens if you would rather prepare your meals. They only offer a 2-tank morning dive but with unlimited shore diving from the house reef. The shore diving is supposed to be very good but I am told that you can often get "winded out" in that area of the island. We have visited CC but never stayed there.
There are lots of hotels and condos on the 7MB which is in the heart of all the activity and with night spots available within easy walking distance. Many dive shops will pick you up on the beach or in their van and take you to the dock. Or you can drive to the marina and board.
When we visit the Caymans we like to spend 2 weeks and do a 2-island trip. We spend time on GC enjoying the amenities and mostly shore diving and snorkeling. There are some very good shore dives off on GC with onsite dive ops like Turtle Reef that only charges $15 for a tank and weights. Some of the more popular shore dives like Devil's Grotto and Eden Rock have really been beaten up by cruisers and other tourists and I wouldn't bother with them. You should experience Sting Ray City at least one time but get there early before the cruise ship passengers arrive. Sunday morning is usually a good time to visit. Don't bother going to Hell - it's not worth it!
We spend the second week diving on LC or CB so we get to enjoy the best of both worlds. On GC I suggest renting a car. There is a lot to see and do on the island. On LC and CB we usually rent a car for one day just to explore the islands.
But there is one other option that a dedicated diver should consider. The Cayman Aggressor is an excellent liveaboard dive experience. Although you will often be diving sites that are available to land-based operations you will get to do a LOT of dives on the best sites available off of all 3 Cayman islands. It departs from Georgetown Harbor on Grand Cayman. Not much night life on a liveaboard!
We did the Cayman Aggressor trip several years ago and it remains one of our favorite dive experiences - but we were lucky and had great weather and spent most of the trip on the Bloody Bay Wall off LC. But keep in mind that if the weather is bad then the boat won't cross from GC to the sister islands and you will be stuck living on a boat that is diving the sites closest to shore on GC.
The Caymans are expensive (the US dollar is only worth $0.80) but there are ways to somewhat mitigate the costs. On GC we stay at the Turtle Nest Inn apartments in Bodden Town which is away from the pricey and popular 7MB and in the middle of the island, but on the water and with good snorkeling right out front and easy access to the entire island. The rental price includes a car which I think is essential on GC. We do some of our own cooking which helps keep down the expenses. We mostly snorkel and shore dive and relax on GC.
But if you like restaurants, bars, clubs, shopping, and nightlife then West Bay and Seven Mile Beach are the best spots for you.
On LC we stay at the LCBR, on CB we stay at the CBBR and both include accommodations, food, diving, airport transfers, taxes, and hotel service charges. The only thing not covered are the dive shop tips (and the bar bill unless you buy the alcohol-included package.)
The Caymans are a first world country. They have good roads, fine health care facilities, low crime rates, good mosquito abatement programs, and the locals are friendly and speak English. Sometimes you get what you pay for!
Have fun in the Caymans!
The differences (for a diver) between the 3 Cayman islands - Cayman Islands Forum - TripAdvisor