What is there to do in Belize, Mexico?
I did a cave tubing and zip lining excursion through the cruise line (NCL). It was expensive but such a great time. It was an all day excursion and including bus transportation and lunch. The excursion was on the expensive side and you can reduce the cost by doing just cave tubing or just zip lining instead. I would not recommend using this port as a "just wandering around" port because Belize City is rather scummy. I would take a cruise line sponsored excursion.
@texassea, Lots of great tips on what to do in Belize here: http://cruiseline.com/port/panama-canal-central-america/belize-city-belize
Ambergris Caye , Belize is a beautiful place , I spent 3 days on that island , I would love to go back