Owing in part to the many varied cultures that have settled this Central American country, Belize is a religiously conservative nation. (There’s even a significant population of Prussian Mennonites who are among the most traditional and conservative of all.) The majority is Roman Catholicism though, as would be expected for the region. There is not much of a local gay scene, which means there are no advertised gay venues, clubs, or events. Concierges at the international hotels will certainly have suggestions of things for you to do, but in general there will be no explicitly-gay options.
That being said, Belize is a romantic and adventuresome destination where you can lounge in luxurious accommodations with a lover, or explore caves and go deep-sea diving with adrenaline-junky friends.
Public displays of affection are frowned upon for all couples, straights included, so keep your hands to yourself and avoid the conspicuous in favor of the generic. The solitude and tranquility of the natural Belizean geographical features will leave you breathless though, so don’t let that small setback keep you from visiting this idyllic land!