Just read up on all this "marriage" talk. I wondered about it for a while also, as I THOUGHT I might end up travelling down that road. Not the case. After living there for 2 years, I have to say...the men are smooth, charming, fun, and very used to their current life style. If you choose to take the route of marrying a Belizian, my only advice is that you ask around about him. If most of the islanders laugh and say "oh, so you know him? Hahaha" this is a good sign to ask a few more questions, such as "how many girlfriends does he have?". Not to be mean and categorize the men, but a lot of them prefer NOT to be monogamous. But, there are also several very good, kind, fun, incredible men down there who are perfect.
As for the visas and such, you can get a residency without marrying someone. You don't NEED to marry someone to live down there. Just so you know.