Clearing C&I at Cruz Bay is usually much more efficient than at Charlotte Amalie where you'll have to wait quit awhile if they are clearing in a BVI ferry. It's also so much easier to access. Tie up your dinghy to the right side of the National Park Service dock and it's 100yds to C&I trailer. Grab a mooring at Lind Pt or anchor in The Creek as Rick mentions (there is usually room for 3 boats, sometimes 4). I can usually be in and out of Cruz Bay in less than an hour including dinghy rides and a quick trip to Dolphin Market (or The Landins for a Bushwacker).

Depending on how much provisioning you need to do, the nearby Dolphim Market is a short uphill walk and handy for topping off on needed supplies.

In STT I don't feel secure leaving a dinghy unattended tied up along the waterfront. You could anchor in Long Bay and dinghy to CYOA dinghy dock, which is secure, inexpensive (~$10), and 400 yd walk to C&I. From Crown Bay it's a hot 1.1 mile walk to C&I (or $30 roundtrip taxi). The Pueblo market near the marina will likely have most of your basic provisions and beverages. I would probably consider Moe's on the waterfront for provisioning much higher quality steaks and seafood, plus produce and speciality foods not found at Pueblo.