Vegas is the mecca for Kite Ground Boarding. There are a half-dozen dry lakes around within an hour of town. Check out http://www.sbbb.net
for details on the premiere local event that takes place at the end of this month.
Windzup is proud to be sponsoring the first annual KGB Throwdown, a kite freestyle comp, at this years SBBB.
Idaho has a few spots, I've mostly spent time on the boards in grassy parks around the area. Salt Lake City is a couple hours from Twin Falls and offers miles of Salt Flats to ride, with good wind off of the big lake.