Belize is perhaps the friendliest and most integrated yet diverse of all of the countries I have visited. The ethic mix is impressive and ranges from Guatemalans, Europeans, Chinese, and Indians that have just immigrated to those that have had roots since the days of British Honduras. Surprising however is the integration of the cultures one finds in Belize; although a place like Hawaii has equal diversity, the integration is lacking. Perhaps it is the Belizean sun which equally tans all or the combination of languages that merge into a barely discernable Creole English, but just to see the integration the country is worth a visit.
Ethnic diversity, according to 2000 Belize govt. survey: Mestizo 34%, Kriol 25%, Maya 11%, Garifuna 6%, Spanish 15%, Mennonite 3.6%, Indian 3%, other 3%
Disclaimer: I spent very little time in Belize, so the sample size to gather this impression is statistically irrelevant. Also, staying in Belize for extended periods of time will bankrupt the average Central American backpacker!