I find it more amusing that everyone assumes the girl is "working" if they're with a tourist.

Both of the times I've been to Jamaica I've met local women my age(26) and both times they didn't ask for anything. That said I definitely paid for dinner/drinks, but that's the same as if I was at home.

Are there women selling themselves? Definitely, but it happens in every country and every economy in the world and it needs to be legalized and regulated.

People really need to have "rules" laid out for them when they travel?

I could see if it's some obscure law in a country that you might not know about, but really just use common sense especially when you're traveling solo.