I was about to answer but looks like Ohio Buckeye pretty much covered it all, great info there
I definitely agree with 3 dives, it is literally right next door and it is always my first meal when I get to Negril, love that place. Xtabi also has just about everything you could need, good food, good drinks, good view.
The little convenience stores he mentioned are nearby and provide pretty much all you will need especially because the superior rooms dont have fridges or microwaves or stoves you probably wont be loading up on much food.
The only ATMs I know of are downtown, one next to Hi-Lo (only has Js) and the other is almost to the roundabout at Scotia Bank, they have two doors and I think its the one on the left that offers both Js and US dollars. Then there is another one at Times Square that offers US dollars but quite the atm service charge.

Also we were able to walk to RockHouse and Pushcart very easily from Xtabi and enjoy meals there too, a little higher end but there are plenty of places nearby, you can't go wrong staying at Xtabi.....enjoy!