Cozumel is a very nice Island. There is so much to do here, you can not get it done in just 1 day. Make sure you stop by Mr Chile's for some really good Mexican food!!!Here you will run into allot of friendly Mexicans with all kinds of ways to get small tips from you. If someone lets you take pictures with their birds or other exotic things you don't see at home, slip them a buck or two. It's not much to you, but a full meal to them. They are aggressive here, but harmless and will take no for an answer. There is a strong police presence here and it feels very safe.
Playa Del Carmen is a nice area. Very pretty water here. The main shopping area is like a giant flea market, except everyone is trying to get you in their stores. Even the restaurants have people posted outside to bring you in to spend your American dollars there. They try hard, but most will take no thank you for an answer and move on to the next person walking by. Do not feel threatened by their aggressiveness, they are only trying to make a living and are harmless. There is a strong police presence here and they keep everything safe.