For a first timer I'd stay in town, The Mayan Princess is a great place, center of town and the nicest balconies on the beach. I think Banana Beach is to far from town(about 2 miles)
Another good choice would be The Blue Tang, which is on the South edge of town and about a five min. walk to the center of town.
Where ever you stay you'll have a great time!!
From a middle 50's guy!!