Carnival has lots of ecological tours offered. Go on-line to the Carnival site and customer service, request a copy of their tours for your itineraray and have them faxed to you. The Legends tour offerings are about 17 pages long. This is the type of port as is Colon & Belize, that a tour would be the right thing to do. Venturing out on your own seems to be discouraged at these new under developed ports.
Are you sailing at the end of February? The ship is really nice. Can't wait to sail on her in April for the same itinerary.