My tip would be to try if you get the opportunity to dive the Cenotes. Mexico has the best Cenotes in the world and it is a truly unique and fantastic experience. I was given the chance to dive them by Dressels when at the Iberostar, it's an early start but it was a great day. This would be my tip for a diving trip to Coz, I would love to spend a couple of days diving them some more, maybe not everyone's cup of tea though but a great experience that is worth trying.
Have a great trip and safe diving. I'm off to the Maldives in a week and looking forwards to getting back in the water.
Tuss, do you have a DAN policy ?