Hi BZ,
I know that San Pedro isn't the best diving in Belize but it is so much better in Coz.
You said that you were staying at an AI. Take some time and venture into San Miguel for some of your meals. Top on my list is Pescaderia San Carlos. Some of the freshest seafood I have ever eaten. I really wish they were open for dinner. El Foco is a good taco place as is Los Oates.
I disagree: Cozumel is much better than Belize! I've been to both many times.