Nothing I'm suggesting here is cheap...LOL.
Maldives if you can afford it. The Four Seasons hotels are pretty nice. The header page for Landaa Giravaru is a Manta Ray so they must be seen often. There's also Kudu Hiraa nearby - and they have their own upscale liveaboard to take you between them - it stops at tiny atolls en route so you can dive/beach. On my bucket list...
http://www.fourseasons.com/maldiveslg/
Jade Mountain above Anse Chastenet is even nicer - and pricier. I can't speak to the diving there. Except Superman's Flight makes a lot of people's bucket list.
Rosewood Little Dix Bay on Virgin Gorda is exceptional - priced accordingly. So is Biras Creek but it's harder to get to (boat/helicopter) and diving is more difficult from there. Virgin Gorda has some of the nicest beaches in the Caribbean - some only accessible by boat. Little Dix offers a honeymoon day where their yacht will drop you two on one with lunch - totally private - there's no road to it. Rock Cafe nearby is one of the nicer restaurants there. There's only about 3K people on the island so it's pretty uninhabited. Always windy and very yachty. DiveBVI is one of the better dive operators we have ever used. It's good shallow diving with quite a few interesting dives - the Rhone, Chikuizen, they have a a small wreck alley now. Not a lot of depth though. All soft corals and fans.
Amanyara on Providenciales, Turks and Caicos - looked very nice. They have their own dive operation and a good dive about 500 yds. out (and their own boat) There's also all the nicer properties on Grace Bay - one of the nicest beaches in the world. I liked the looks of Veranda - I believe it can even be done as an AI. Outstanding shark filled diving on French Cay or West Caicos but that involves a shuttle to the marina, a 45min. boat ride and lunch on-site. Plan on being back around 2PM or later. 4PM if you do 3 tanks. Outstanding wall diving - off West Caicos we drifted a 6000' wall. Some of the healthiest coral I've seen in the Caribbean and I've been to many of the better locations - on my list here the only place I've not been is St. Lucia and Belize but my regular buddies have.
Beaches suck on Bonaire - I'm sorry but they do. The few resorts that have one make it over the ironshore that fronts their property. The only good beach is Lac Bay on the east side where they windsurf/kiteboard. Any others are ground coral rubble. Most have ironshore offshore so you need surf shoes to get in the water. The only exception is Harbour Village - the nicest resort there - they have a nice beach but a lousy dive. Fortunately good shore diving is just a few minutes away.
Curacao has some nice beaches but no honeymoon grade resorts on any of them. Most would be a short drive away. Lodge Kura Hulanda is very nice, very remote and a very good dive. Average to poor beach though - narrow and mostly rock/coral rubble. It's also 45minutes from anything.
October is the Rainiest month on Roatan. Utila also since it's close by - I suspect Belize and probably Costa Rica also. If you did want to chance it - Barefoot Cay on Roatan is among the nicest combined diving/beach properties. They suppress the sand flies there but they can't do much about the humidity. It's a little industrial behind the cay though. West Bay beach is nice but cruise ship crowded daily.
None of the dive AI's (Cocoview, Reef House, Anthony's Key) have any (or much) of a beach. Fantasy Island Beach Resort does but it's older and though the resort was refurbished this year, the rooms weren't. They needed to be - some friends had problems with dirt, light bulbs missing and no hot water a few years ago. It was cheap but they got what they paid for.
Utopia Village is the nicest of the AI's on Utila. I've stayed at Deep Blue, the rooms are sparse, average and two double beds. Their beach is very narrow and fronted by ironshore/coral reef - there's only one spot you can even get in the water and it's over rocks and requires dive boots. I liked it there for diving/whalesharking but it's a small, remote resort. All 3 AI's are five minutes by boat from town.
I don't think I could spend two weeks on either without being bored. Except for the flight it can be pretty affordable though.
In south Belize there's Turtle Inn or Hamanasi. Nice beaches in that area but the diving is an hour + boat ride out - there's no shore diving it's too shallow and flat.
The Marriott Grand or the Westin on Grand Cayman are nice beachfront properties. Dive operators will pick you up there - some off the beach with flat bottom boats - to dive nearby. Others with van shuttles. Lots of excellent restaurants but it's all very pricey, food is high and dives are 2/$100. You can shore dive there also - some good sites within about a 15min. drive.
Actually the other poster makes a good point, October is mid-Hurricane season in most of the Caribbean. I might look elsewhere.