It is a beautiful area and Tres Cocos is a great snorkel. We stayed in the area last Christmas and it can turn a little cool at night that time of year - if you are cold natured bring a light jacket, as Denny said.
Any place is a good place to dance - BC's, Fido's, Mango's, Crazy Canuck's, Hammock House, The Palapa Bar, the beach, a pier, etc.