I haven't checked around in a while, but we have some guests coming in March, and the wife cannot have gluten in anything. Does anyone know of a reliable source of gluten free bread, flour, etc., here in San Pedro or BC?

I think I saw some gluten free flour at the Greenhouse. Try Wine de Vine as well.

while you will find a limited number of gluten free cooking items at Greenhouse, not enough to make a meal. I'd highly suggest if they are looking for gluten free breads to be on the safe side tell them to bring what they like. That is a pretty serious dietary requirement not to be chanced for one with Celiac's.
They will already know that they could enjoy 100% pure meat (with no gluten additives/sauces) along with pure corn tortillas, rice or potatoe/yams or soybeans. Any breads in Belize would be hard to chance it with, unless a special bakery in town can provide they have a gluten free bread processed in a machine where other gluten breads were not.

I would think between many gluten free fruits, potatos, and corn tortillas they will be find on vacation without bread for trip and if not they could bring a loaf or two with them.

We have lived in Belize for 2 1/2 years now and are gluten free (Celiac). You will NOT find gluten free bread, but you will find rice, tapioca, potato, coconut, chestnut, corn flours and starches as well as rice noodles all in Belize City. You are allowed to have potatoes, rice, sweet potatoes, fruits and vegetables as well as meat. The only thing you will really miss is the bread. You can make muffins easily enough, just look up on the internet for some very easy recipes. We make our own bread, muffins and scones, cookies on a regular basis. If you want to private message me, please feel free.