the key is your realtor here in belize. if you are considering buying land in a foreign country, as i did 5 years ago, its IMPERATIVE that before you hit "send" on loads of cash, that you truly TRUST your realtor. They will give you the honest scoop...provided you go with an MLS listed realtor here in San Pedro.
Just because you recognize the name of the real estate company in the states, does not necessarily mean they are the most reputable here in the country. I used www.investinbelize.com
when i purchased 5 years ago, and Tim and Tina continue to be trusted and dear friends to this day.
I've no doubt loads of others will also have opinions, but to answer your question - no, there is no place to compare average prices....not to my knowledge anyway...