My wife (we were there on our honeymoon) and I just got back after 8 days in Isla Mujeres and our evening at Maria's Kan-Kin for dinner was definitely the highlight our of restaurant experience. Before our trip I was able to get the e-mail address for Sabestian and coordinate a beach-side dinner for us. He was very responsive and even tried to help answer some additional questions I had about the island. We stopped by a day or two before to check it out and knew that we had made a good selection for our big romantic dinner.
When we got there for dinner, they had a table set up on the beach with candlelight. The food was fabulous! Everything from the calamari and guacamole topped with shrimp tostadas for appetizer to the hog fish and red snapper for dinner were fabulous! Sebestian also prepared us a special dessert that was out of this world. His now fiance (congrats), Agostina, is in charge of the service and even prepared a special drink for me after I was asking if they could make it. She was very nice to chat with during our meal too! They also announced that the re-signed a contract with the hotel (which is currently for sale) for another year!
PLEASE go visit this restaurant while you are on the island, if you don't go then you are seriously missing out. It is near Punta Sur and I believe they stop their dinner service around 7pm or 8pm, but this is well worth your trip and the views are amazing! Stay away from the centro and go explore the island, you may just find this hidden gem.
Thanks for a great night!
-Chris & Sidney