Let the hive mind of Engadget get that for you.
"As someone who doesn't reside in the USA, I was wondering what would be the best way to get internet for my computer in the US for a couple of weeks? If it were Europe I know I'd look for some prepaid data. Is there anything similar offered by American carriers? A MiFi or a data SIM that I can tether from would work, but I'm trying to maintain a tight budget. Help!"
Too bad UMPCs are so expensive when the hardware isn't all that great (compared to laptops). I guess you're paying that hefty price tag not for portability, but ultra portability. However, if I had the money to throw away, I'd definitely throw it at this.