Even if Ziners don't come up with the answers to your questions, you might be able to get help on this message board, which is specific to your destination (this particular thread is on the subject of mosquitos): http://www.ambergriscaye.com/message/Forum4/HTML/000273.html

You might try searching http://www.google.com for Ambergris Caye to see what other info you can track down.

Best wishes from Toronto, Linda