For full out AI, I'd go with the Occidental Grand, beautiful property, cut out of the beach side jungle and mangroves, good food, not the same thing on the buffets day in and day out, ( I'm going on experience from 3 years ago), big, roomy rooms, with safes and stocked bar included, shower and tub for rinsing gear, 2 pools on site. It's very far south so boat rides are short to the reef, but taxi cabs are around $20 each way to town.(the only real drawback)
You may check into Hotel Cozumel also, they have both AI and non-AI packages I belive. A very nice pool area, small beach, they are very close to town, walking distance for sure. Not sure who the hotel's dive is, may be Dive Paradise, but don't quote me.
I think El Cid La Cieba is doing AI packages also, very nice property, great staff and what I think is one of the best proprty locations on the island. Some folks don't like the closeness to the International Pier, but I like the activity. Haven't been out there in a few years, but shore diving out in front of La Cieba at "Airplane flats" used to be pretty good, shore diving on Coz isn't great anywhere, but with some nosing around you can find some pretty cool stuff in the shallows.
to the no-frills side, but still nice properties, I'd look at Blue Angel resort, of course, small 22 room hotel, right on the water, small but adequate pool, nice little restaurant for breakfast, lunch and I think happy hour now, good sized rooms, one of the best dive ops on site, only a mile from town, we walk to town quite often, although maybe not so much in June:shocked2:, it will be getting a little hot by then.
Villablaca gets good reviews, is close to where Blue Angel is located, I think Papa Hogs is thier dive op, but again don't quote me and Casa del Mar is also a long time favorite 'divers' hotel with a faithful following.
Going to Coz, like most places the first time, can be pretty confusing when it comes to picking lodging. Stay out of the Northern hotel zone, as most dive ops can't afford to spend the gas to go up there for pickups so, they will require you to take a cab downtown to meet up with them, that can add up quick.
Narrow it down to a few properties that seem to have what you are looking for and pick one, then while you are on Coz, take notice of where the others are at and maybe even stop by the proprties check them out to see if you might want to make a change on your next trip...Oh yes, there will be a next trip :d