I would go to the beach at Majahual (sp). Its about 2 miles from the port. You can get a cab (approx. $3) there or rent a golf cart ($15/hr) or walk (while some people did this it was way to hot for me and I wouldn't recommend it). There's a really nice beach there and you can rent waverunners, go for a banana boat ride, parasail, snorkel, etc. There are restaurants and bars along the beach. You can even get a massage right on the beach there. The vendors in town are a bit agressive, but once you get on the beach they don't bother you much. We've also been to Uvero beach and I think the beach at Majahual was nicer (and cheaper).