tosh is correct; the LV in San Juan is too far to walk from the cruise port. It's in the posh neighborhood of Coronado, about a 15 minute taxi ride from Old San Juan where the port is. It's an area with lots of hotels so you don't have to worry about finding a taxi back. And yes, a sales tax is imposed on LV. I remember it being between 5.5% and 6.5%. This practice didn't start until 2006 when the U.S. government decided to levi sales tax on the commonwealth. The SA's are pretty nice, but they don't seem to know too much about the product line. I ended up getting a thank you letter from the SA that helped me when I returned to the U.S.
Enjoy your cruise!