My wife and I spent 5 days at the Renaissance Carambola in early March and absolutely loved our time there. To maximize the length of our visit, we spent a night in San Juan and flew in early on Saturday morning, taking a ~$35 taxi to the resort. Upon arrival, were were greeted by the very hospitable front office staff. While I had asked for an upper level room, we were given a ground level room that was great - the units are so well set and private that it didn't matter.
The resort is surrounded on 3 sides by mountains and by the ocean on the 4th side. Our unit was located about 50 yards from the beach with a long green yard in-between. In the unit was a very large bathroom, a sitting area, a large closet and dresser and the screened-in patio - it was spacious and well-appointed.
The beach was great - lots of soft sand, ample lounge chairs and palm trees if you wanted to get in the shade. The surf was not too rough - we saw many scuba divers going off and coming back right to the beach. There were no noisy boats, hawkers or loud people or music - it was very relaxing.
We ate at the restaurant at least once a day, typically for dinner. The menu was small, but had lots of variety and the food was tasty. Prices were below what we've paid at other resorts and the service was excellent.
We did some fun things around the island. In Frederikstad, we went spent a very fun and relaxing afternoon at Coconut's Beach Bar just north of the pier. We also went on a great kayak tour of the salt bay with Virgin Kayak - highly recommend them. We also spent a fun afternoon in Christianstad. If you're into shopping it's worth visiting.
All told, we would highly recommend this resort and St. Croix, overall.