Cozumel:
Not much to see if you don't dive. Then LOTS if you do. (Dive with Living Underwater. Steel tanks. Best operation on the island, hands down.)
No need for a car. If you want to "get around" rent a scooter for a day. You can go around the entire island in about 2 hours on it. Car will have no use to you.
Cabs are pretty easy to get and cheap. If you want to grocery shop, cabs are still easiest way to do that.
Last time we stayed at El Cid. Decent place. Decent pool. No beach. It's part of the RCI time share. It's also on the way to the dive locations so short boat ride.
Some good resturaunts on the island but ask around. Most of the really good ones the locals know but are not heavilly advertised. They are also generally not on the main road. (There is one that good there. A place that makes wood fired pizza. But other stuff on the menue is better.)
Myan ruins are decent if you are into that sort of thing. But they are ruins, not full pyramids.
Zip line is fun but short.
If you get a scooter for a day, circle the island and stop on the "other side" at the resturaunt on the beach. Decent food but amazing view and you eat out on the beach.
Anyway, check on line for deals. You can usually get El Cid rentals super cheap.
