This article in the Economist is worth a read.
"The latest migration is from elsewhere in Central America. Thousands of Salvadoran refugees arrived in the 1980s. More recently, Guatemalans have come seeking land. Of Belize’s 300,000 people, 15% are foreign-born. Thanks to higher birth rates, mestizos have overtaken creoles (of mixed African ancestry) to become the biggest group, making up half the population."
Changing geography in Belize and its effect. Elizabeth Allen
Via Best of Cayo