I'd like to chime in in favor of Andros Island and Small Hope Bay. It was where I did my open water certification back in 1998, and since then I have been diving in Hawaii (Kauai, Maui), Cozumel, and the British Virgin Islands. I still consider Andros to be my most enjoyable dive spot: it is laid back, the food is very good, the comraderie with the other guests is high, and the dive operation is great. The oceanside cottages are rustic and comfortable- you just have to watch out for the falling coconuts on your strolls up to the lodge. Each evening over conch fritters and beer you are told the options for the next day, and they are pretty flexible. The reef is quite extensive and definitely not picked over very much. There is almost nothing else to do on this island, so if you don't miss the cruise ships (I don't- Cozumel had too many of them swarming around, imparting that "cruise ship mall" feel to the place), this is a good spot. I still regret not doing the "Nitrox Special" 190 foot dive they do each week- a few minutes on a shelf hanging over the Tongue of the Ocean getting buzzed, then up you go. Snorkeling off of Sheep island was the best I've ever done: acres of staghorn coral swarming with parrotfish, about a mile off shore- they were willing to dump us off the boat out there, which was an odd feeling (like walking the plank).
Yes it is pricey, but it is a memorable and worthwhile experience I hope to repeat in the future. Everywhere I go I compare to Small Hope Bay, and it still ranks up there for me.