I was in the port of Belize last year jan 22 on th ncl sun, my thoughts are to either book something either on line or through the cruiseline we went off on our own and we just went on a little car tour with one of the locals it was 8.00 each there were 4 of us he took us on a 70 minute tour some places were quite nice landscape, but it is a poverty striken place and the children beg for 1 dollar or two dollar and make up stories of there parents being dead or in hospitals etc. and they need monies for them, I would steer clear of jogging out on the streets althrough there are quite a few shops if you are going to Cozumel save your shopping for there also Roatan was the same way!! I plan on staying on board ship this next round of ports when we hit Belize, been there done that and do not want to do it again, Ill spend the day in port at the pool it will be empty, and eat and Drink and use the hot tub as it to will be quite vacant, not to mention the great waterslide on the Miracle, there ar some good deals on excuration on some of the websites...........
http://www.actionbelize.com/index.htm check them out and seem very reasonable