Just double-checked the customs form visitors are given on the airplane coming in or at the airport, and the specific legal limit is one liter of spirits or one liter of wine.
However, as a practical matter your luggage may never be checked (Belize now has a green/red customs system) or if checked the customs officer may not be strict about alcohol for personal use.
Beer is a special situation due to the legal monopoly Bowen & Bowen has in Belize for Belikin. You cannot bring in Mexican or other beer beyond a bottle or two for personal consumption. If Mexican beer were legal in Belize, Belikin wouldn't be around for more than a year or two.
--Lan Sluder www.belizefirst.com