Well; there are many solid pieces of advice in this thread.
I would only add a couple of things, and I may get roasted for them.
First of all; if you have a compromised immune system or irritable bowel syndrome or anything related do not eat at the roadside barrels/stands unless they have a supply of clean fresh water to wash hands and food, and some ice on hand to store their product.
My wife and I were sickened by a very popular west end jerk stand guy (who is no longer with us), who served questionable chicken.
Others on this board have raved about him, so sometimes you can't really trust everything you read.
Don't carry any gov't issued I.D. on you. Just photocopy what you have and keep the real thing in your room safe or hotel's office safe. The photocopies will I.D. you in case of an accident.
Place your cash/room key in a zip lock baggie and put it in your swimsuit pocket (men) or add a little coin purse to the zip lock ladies and safety pin it to your top strap.
Eating at Burger King is not sacrilege. The fish Sandwich is Jamaica caught and the burgers are Jamaica beef according to the posters on the walls.
It's just a money-saver on occasion if you are so inclined and they have good A/C.
So does Juici Patti past the roundabout. I love those patty deals at Juici; often two beef patties and a drink box for 300 J, about 3.75 North American.
The bonus is you get to dine with the locals. Kids in school uniforms; moms and babies; cops; armoured car guards who prop their automatic weapons against the wall, everyone!
Don't negotiate with the taximen parked along Norman Manley Boulevard. In other words don't ask how much the fare is; You say, (if you're going from beach to a cliff resort) "How about 500 J to Catcha" which is about 6 dollars; which I have determined pretty close to fair. Walk away if they say no. Someone else will grab it or the guy will relent and say O.K.
Tell cab drivers you want a slow, safe ride and they will comply.
I've had idiots try to break the land speed record and I just tell them to 'One Stop' and get out of the cab.
As many others have stated; you can have the route cab experience (after establishing that you know the going rate first); but it's really not necessary.
To travel the distance of say the Margaritaville area to deep west on the cliffs in a charter cab is only 5 or 6 hundred dollars in the daytime. That's about 6 or 7 bucks which in your hometown would be an easy 20 dollar ride in a cab.