Jerk Chicken- first you have to define it. Are you also talking about "Pan Chicken" which is the barbecue cooked in the oil drums, or the real jerk? For pan chicken, most any of the places along the roads will do. Some spicier than others, lots just pour the ketchup (gasp!) on.
Real jerk- over a smoky coal fire and first rubbed with the incredible spices with lots of scotch bonnet and scallion- is truly hard to find. DeBuss, or now Bourbon Beach (if they're still open and cooking) had the real stuff. Ozzie's isn't bad, but not smoky enough. Bigga's, in Green Island is good, get it on the way.
Dragon Bar- on the Red Ground road, is really good. Worth the trip!
Don't confuse pan chicken with the real jerk!
Dave