A lot of that depends on what you like to do. Personally, I'm very comfortable on St. Thomas. If you just want a beach day, there are cabs to Magen's bay, emerald beach etc...... End quote
Poormom has a good point for St Thomas. Cab to the beaches is fine. I have a tip however, Going out is easy to find a cab, coming back is NOT easy to find a cab. So ask the driver who takes you out to come back at a specifed time. Give him a good tip on the way out and you will be set to come back. Be ready at the appointed time. BTW I thought Meagans Bay was very nice. Going up the skyway was fun too, don't need an excursion for that.