Try boards.cruisecritic.com? Lots of forums, usually with up-to-date discussion about exactly the things which you're asking about.

I understand about C&C's. But don't forget that it's there in case you do manage to get away by yourself. If you're on the Sun and she docks at her usual place, C&C is just over the road from the pier. However, I have a feeling that everyone will still be tendering by the time you get to Cozumel.