The only diving "near" orlando is cave country, with some nice cavern dives if you are not cave certified. This is about 1.5 hours north of Orlando near Gainesville. A good site to look at is for a shop called Birds Underwater in Crystal River. They have descriptions of the major springs with links to each spring's website, and they also have a some sites/wrecks in the Gulf of Mexico that they can do. They are a truly first-class op.
If you want truly world-class ocean diving, the best bet from Orlando is the West Palm Beach/Jupiter area. It is really spectacular diving with excellent reefs from 50 to 90', deep ledges at 130' that often have huge marine life and sharks, and a great assortment of wrecks at all depths you could want, shallow to deep. The Gulf Stream is very close to shore and you can be in the clear blue water 2 or 3 miles out with 150' vis. Typically, usually runs 60'-80' or so. A really bad day is with 30' (still not bad), and any worse means that the seas are too rough and most operators wont go out. There are shore dives if you want, and the Blue Heron Bridge is one of the best macro/muck dives anywhere in Florida.
As you go north from West Palm, the gulf stream moves many miles out, the reefs largely disappear, and you are limited to rocky areas and maybe some wrecks. There might be the occasional nice spot but relatively few.
West Palm is truly world-class diving. I know it is a ways off from Orlando, for two days of diving, you would want to overnight in West Palm. I can tell you, it is worth it. I am from Ft. Lauderdale and regularly (2-3 times a month) make the 1.5 hour trip to West Palm. It is basically all drift diving (even the wrecks), which makes your descents and ascents much easier and the reef dives effortless. Lots of top shops and operators.
The Keys are great, but a very far trip, at least 5-6 hours to Key Largo and add another 1-2 hours to the lower keys.
