Tmbm: I don't use a card, guess it's internal in my laptop, which is 1 1/2 yrs old - maybe you don't need one either. What I use for Wifi is ATT, which is partnered with Cingular, and I originally paid $20 a month for one year - now it is just $2 a month. Where I get online is most often McDonald's, but Barnes & Noble and UPS Stores are also hotspots. The signal is nearly always good enough to pick up in the parking lot, and the part I like best, besides the price, is the 800 number that's answered 24/7 by a person - wow! They can tell you where the hotspots are in whatever city you're in, or help if you have any problems connecting. Most of the time the speed is acceptable, even for me, and I have ADD, which means I don't like waiting for the bleepin computer to DO something, lol.
If you're in a bigger truck, some places may be hard for you to get into, but in a cargo van, I think ATT is the best deal out there.