The UMTS/HSDPA stuff from Cingular is marketed as "BroadbandConnect". I just got a card last week (and a sweet new 2125 phone) that I can't really use yet since my laptop hasn't arrived. No comment on how it performs yet (can't wait to try it vs. EVDO which I've used from Verizon)
From Cingular's website:
BroadbandConnect service is available in the greater metropolitan areas of Austin, Baltimore, Boston, Chicago, Dallas, Houston, Las Vegas, Phoenix, Portland, Salt Lake City, San Diego, San Francisco, San Jose, Seattle, Tacoma and Washington, D.C.
So yes, Vegas and Austin should have some sort of coverage.
http://www.cingular.com/sbusiness/umts