YOu will love the port, at Roatan take the ski lift to the beach for 5 dollars a person or walk for free. At Costa Maya take a taxi to mahalajua, it is 5 dollars round trip, 2 there and 3 back. It is (or was last yr) a beautiful very rustic mexican village. We loved it. oh and get a massage on the beach 10 dollars for 30 mins or 20 for an hr.
cant help you in belize, I am not even sure there is a clean beach you can walk to. But be sure to watch the ship arriving in Belize and see the tiny little islands the ship has to dodge. It is beautiful. Have fun!!!