PlanoAg98 said:
Get a guided golf cart tour of the island if you've never been. They'll take you to all the best bars/restaurants to eat and drink all afternoon while not having to drive. There are some pretty good hole in the wall places you'd never go to as a tourist alone.
Excellence Playa Mujeres is north of cancun on the mainland, not on Isla Mujeres. But your point still stands.
The best excursion we took was the Excellence customer only giant catamaran trip out to the island. The island and the beaches were beautiful. Buy a bucket of beers and enjoy the beach, get your drunk self shipped back to the resort and drink some more.