As Mobile Burn points out, you can go to Cingular's coverage map and zoom in close to see if you have 3G coverage. Alas, Minneapolis is not included. Next time, Cingular, just give us a list, hey?
Cingular has not posted a list of all of the covered markets, but you can use their online coverage map system to check whether or not your part of the country has 3G service. Once you are zoomed in on the map at the City level or closer you will be able to check the "Show 3G Coverage" checkbox to see if UMTS coverage is available near you.