In Negril, most of the locals who will greet you are higglers who will try to sell you things (any and everything). Usually a fist bump will suffice. If you are not interested in buying anything from them don't stop to fist bump or chat, just keep walking and smile and say "not interested" in a firm but friendly way! Never say anything like "maybe later" or "not today". To them, that means you will buy next time they see you.

If they try to hand something to you to look at don't accept it. You hold onto it you buy it. Don't let them put a bracelet on your wrist without your permission, it is a scam.

As far as your girlfriend is concerned. Any unwanted physical contact or inappropriate sexually suggestive verbal dialogue would be crossing the line, just like home.