I think you should pack your bags and go ... right now

Summer is great because because Negril empties out of most of those American tourists. It's quiet and empty (except for first week of August when it fills up with Jamaicans on holiday). You can bake and relax in the summer heat. You get a smattering of European tourists, plus the locals. Even the local peddlers and hustlers and prostitutes slow down in the summer heat, with fewer clients to chase after, and you can hang out with them and chill and get to know them as people.

That said, any time of year is good.