We had very good luck with SailCaribe on a PR/SVI charter in 2012. Probably the best service we've ever had from any charter company. The boat (Lagoon 450) was in like-new shape.

I recently inquired about sailing from Scrub Island, and was told that all charters must _end_ in Fajardo, but you can start on Scrub Island or Crown Bay, St. Thomas. There is a one-way charge, that I think is basically the cost of delivery to STT or SI. Unfortunately that's not what we had in mind for this charter--but it might be perfect for the OP.