The HPWCs are in the Northpark Mall. I don't know of any at the Galleria. Note that they aren't a full 80 amps. I think you'd be better off at the Service Centre's HPWCs. the Service Centre is in the general area of the Galleria, on Welch Street, just south of Spring Valley Road.
Going north on 75 take the Spring Valley exit and turn west. Drive a couple of block to Welch and turn south. It's on the west side of the street.