i liked cayo coco a lot. Its a lot quieter than varadero. NOt as much to do, as its isolated on its own little island. Just resorts and sand. Nothing local. Nice though, especially if you like snorkeling.
Also some solid fishing from shore -- bring your rod. Or take out one of the sail boats out just off your resort, drop some shrimp (get them from the resort kitchen) and hold on. One of the guys from our resort caught a BIG snapper.....only landed its head though. A shark bit off the rest (not kidding)
Also funny -- at our resort (and i'm sure others) there were wild bulls walking around at night.