Here's a decent set of maps online from the folks at Isla-Mujeres.net;
http://www.isla-mujeres.net/maproom.htm
Some of my personal favorites are for casual food and drink are Jax, Buccanero's, Rolandi's, and do try the west (Cancun side)open air, restaurants near the pier serving cold cerveza and fresh grilled fish.
Garrafon Eco Park is a terrific day trip, Castillo adjacent to Garrafon is a good do on your own snorkel& sunbathe venue also and Playa Norte is one of the nicest beaches one will find anywhere.
The Turtle Farm is a must see in my opinion, the Pirate Mundaca Park so-so, the Lighthouse and shops at Punta Sur worth a visit (do climb the lighthouse for the view) and shell collecting on the eastern shore can be fun but you'll need to get there early.
Also, just wandering the town center shops and restaurants can be a lot of fun as well.
Keep in mind there's plenty of snorkeling and scuba opportunities available as well.