We stayed at the Caves for a few nights during our honeymoon... its AI, beautiful, very romantic, extremely peaceful but it is a bit secluded (for us, that was a good thing). That being said, you can definitely leave the resort and easily find some action. The Rockhouse is definitely bigger, and its bar/restaurant is open to the public and gets a bit of a crowd, but not AI. If you are looking for something with a club, etc, the Negril cliffs just may not be your thing.
We also stayed at Sunset at the Palms, which was beautiful, few kids, AI, but the bed was actually REALLY hard - to the point of being uncomfortable. I don't know if that was just our room, but I thought I'd put it out there. They do have crazy bathrooms with 2-person multijet showers, which was pretty cool The food at the beach and buffet were good, the restaurant wasn't. The staff was friendly, fun, and very helpful.
We also stayed at Jakes in Treasure Beach, and got married at Coral Cove in Little Bay. They are both quiet, secluded locales. If you want more info on them, let me know.