I.C.
Negril is the place to go in Jamaica. I've been there twice-To the Sandals resort years ago and just last year with the whole family to the Riu resort.
http://www.sandals.com/main/negril/ne-home.cfm
And
http://www.riu.com/en/clubhotel-riu-negril-jamaica.html
The second link is for the place we stayed last year. It was more affordable, but it is a resort for couples, families, singles and groups. When we were there during spring break last year, it never felt like there were alot of people. The beaches were always half empty and I didn't feel crowded.