ggunn, I enjoyed your review of Cozumel. What hotel do you usually stay at? Many divers don't care as much about luxury settings, but are there for the diving. I last went to Cozumel in '95 and stayed at a hotel (I think it was Hotel Colonial) along the walk-way from Prima to townsquare with a balcony on the end units overlooking the walkway. They weren't luxury, but there were decent and had a refigerator and a small stove-top. It was very convenient to town square and all of the great and inexpensive restaurants. We dove Blue Bubble, which was just a few blocks away. I was very impressed with them, especially our DM Raul. I wasted 11 years of living in Dallas while being certified before I experienced Cozumel. It is a bit more expensive to fly to Cozumel from Cincinnati then from Dallas.
On the wetsuit questions, I dove in July '95 with no thermal protection with no problem. I used a 3mm shorty in November and because a shift in the winds, I was VERY CHILLED. When the winds shifted back to normal, the water was calm and my shorty wetsuit was plenty to keep me comfortable. It is nice to have warm air during the SI. If you get chilled at all, it would be good to have thermal protection in the winter months.