My husband and I went on our first cruise on the Ecstasy (Oct 29, 2007 through Nov 3,2007.) We decided we wanted to go see some ruins in Progreso. We chose the Uxmal excursion. It was so worth it! They really are beautiful and interesting. Lots of big iguanas! The guide was informative (he has been studying the ruins himself.) We were able to climb on and enter most of the ruins and had some time to explore on our own. We were very happy with this trip. Definitely wear comfortable shoes. The terrain was rather rugged.
-on trips to Mayan Ruins in Mexico, I would always recommend to take tours first and then on a second visit maybe go on your own. These guides are federally certified and have basic and some incredible knowledge and point out details that one would miss on his own and makes the entire experience more "magic". Backpack with sunscreen, hat, water bottle and steady shoes, of course adequate clothes are recommendable as well as camera (fees are charged for video cameras, not foto cameras) and some cash. If not included, a granola bar and some sugar is also a good idea as well as mosquito spray...hope this helps!