Just returned from a stop at Costa Maya. We took a taxi to a local beach but its pretty rustic and the natives harass you to buy junk. You're better off doing the Jungle Beach excursion with the ship. Otherwise, the pool located off the pier is beautiful, free, and you can sit in hammocks by the water. Local Costa Maya isn't really ready for tourists yet - we took a local snorkeling trip and ending up haggling over the price due to a supposed misunderstanding from a language barrier (they didn't speak English).