We enjoyed our week at Casa Sora. It's a big comfortable well-equipt house in a quiet neighbourhood, near grocery stores. The pool was clean and refreshing!
Maria, the cleaner, was lovely. Fred met us at the ferry and was patient and helpful while we rented our car.
San Miguel is a bustling touristy town, but there are some great restaurants (la Choza!). The west coast of Cozumel is built around the cruise ship industry, with beach clubs catering to passengers who arrive en masse via taxi. But the east coast is spectacularly beautiful and unspoilt (about a 20 minute drive). The undertow can be strong but we found a great swimming beach at Chen Rio. Punta Sur .. at the southernmost end of the island... is also worth a visit.