I'm planning a trip to St John and St Thomas with my DH and DD12 next June and I happen to have a map of St Thomas that I bought. I would say the ferry dock location is in Charlotte Amalie (ferry goes over to St John). The cruise ship location is probably in Havensight - it appears by the map that that's where all the cruise ships dock so I would say you're right. You might want to take a look at Dependable Car Rental. I think they'll pick you up at the cruise ship dock and after you return the car to their location they'll bring you back to the dock (all for free I think). They're local and seem to have a pretty good reputation from what I've read on some of the travel boards. Their website is www.dependablecar.com if you want to check them out but you'll have to e-mail for rates. Because they're not a the dock it may not be as convenient for you as Avis but it's another option anyway.
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