The most efficient way to get specific info about current (my experience is 10 or more years old) access solutions is to have your travel agent (?) contact the Port Authority in St. Thomas for information or referral to the business you wish to have access to. I visited St. Thomas twice, took my scooter and my Service Dog both times. Of all the island nations I visited, St. Thomas was my favorite. If you are taking a Service Dog, be prepared to be charged for a second person in a taxi. There are also strict rabies vaccination requirements for Service Dogs (mostly for the protection of the Service Dog...native island dogs are everywhere and do not always have the best manners). Accessible taxis were available, but not common, and you might find yourself being hoisted into a pickup truck or an open multi-seat sightseeing caravan-type bus, if wheelchair use is your access challenge. BTW, steps are everywhere, not ramps, and it was not uncommon to join the crazed automobile drivers in the road to get from point A to point B. Have fun!
Very few of the shops on the main shopping street are accessible, especially further from the water. Bluebeard's Castle has very limited accessibility.