we were at Couples Negril in March 2007...absolutely no spring breakers. You are only allowed at couples if you are a couple..so if there were spring breakers, they would have to be a couple, and it's unlikely that you would get several spring breaker couples to go together.
The couples resort doesn't fit the demographic for the typical 'spring breaker'. College kids usually go to the very inexpensive party resorts. Couples doesn't fit either one of those requirements.
I wouldn't worry. We've been there in March, and we are going back in February 2012.
Couples resorts are for couples only. The rooms are double occupancy only and the prices rather prohibit any spring breakers from trying to "sneak in" so to speak. It's pretty well advertised on any booking site and any travel agent would know to steer spring break kids away from these resorts. So no, you won't find the spring break atmosphere at Couples resorts.
While I am sure Couples Resorts do not discriminate against spring breakers. The whole style of the resorts would not be where they would want to be. The cost is going to be prohibitive for just about any students. We were just there in Feb-March time frame and the place was wonderful. Not super busy and the weather was awesome. We were at CSS, but I assume CN was probably about the same. The night life is what you make of it and if you just want to relax and enjoy being pampered this is the time and place to do it. Don't hesitate. Also check out the youtube videos of the place before you go and that will help you to understand what to expect.