Ask your driver to stop somewhere in Montego Bay to exchange money. Might be cutting it close if you wait until Negril. Don't wont to be stuck your first night with no cash, first night always seems to be the most fun. Haven't been to much of a beach person but we had dinner at the treehouse table I think they call it at kuyaba. A table a story up right on the water and you're by yourselves. Call ahead to see if it may be available. Tough to get during the high season I'm told.
Also count your money right in front of them if they don't count it out for you. I really feel I was screwed over big time once. This of course comes with knowing how much you are supposed to receive. And if you go to the cambio next to Hi Lo the exchange part is in the back of the store. First time I went in I stood in the western union line for over a half hour before I realized it was back there.