Hi, Gwen ...
I highly recommend the trip to Uxmal. The ruins are fabulous. You can see some photos at my personal website, <http://happysails.com>.
The beach at the end of the causeway from the ship's pier isn't much and there isn't a lot in the way of shopping in Progreso.
We will be there in a couple of weeks, so I will update all my western Caribbean features when we return.