How long do you have? If it is only a week or two, you can see plenty in the USVI without going through more red tape (if there is in fact some) to get to the SVI. Also, one of my least favorite sails as a kid was sailing from Culebra to St. Thomas. It was typically straight into the wind and waves and took forever. Of course we were sailors and my parents rarely used the engine (if it worked) so we tacked and tacked and tacked again! If it were me and I had a ton of time, I would plan a trip to St. Croix instead of the SVI.