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!"
I totally got on that att wireless before it was as open by just using a generic username like lonewolf and did the "forgot my password" option and it asked me what my favorite movie was so i put in "the matrix" and i got on the wifi.