We prepurchased a day pass for the British Colonial Hilton. It was a tiny, but nice beach. Very easy, short walk from the ship. This was perfect since we were only in port till 1 pm. We managed to spend about 4 hours at the beach. The lunch was fine, drinks were great. The cost was incorporated into the cost of the day pass. When we first got there, we were the only ones on the beach. The cruise ships are right next to the beach.
We used the St. John coastal tour excursion simply for transportation directly from the ship to St John. It made more sense to us than taking a taxi and then a boat. This was easy. Once at St John we left the tour and took a taxi to Cinnamon Bay. It's beautiful there, but no chairs on the beach. There were restrooms and a decent restaurant for lunch. The area is very rustic due to the campgrounds there. We've been to Trunk Bay in the past and I think I prefer Trunk Bay to Cinnamon, but both are gorgeous.