Well, you can get to Dolphin Market from Salt Pond, but not by walking. There is a bus stop at the Salt Pond parking lot and the bus runs from there through Coral Bay to Cruz Bay. I would treat it more as a $1 ticket to adventure than public transportation. If you needed to get to Cruz Bay to pickup a boat part its a reasonable option.
http://www.vinow.com/stjohn/getting_around_stj/Department of Public Works: 1-340-774-0828
Concordia Eco-Resort is walkable/hikeable, run by the former Maho Campground group, has a camp store and a decent cafe.
http://www.concordiaeco-resort.com/Cheers, RickG
