I'd recommend buying a used Verizon 3G MiFi (about $75) on eBay and then opening a prepaid acct with Verizon. They have several plans for prepaid, its on the expensive side per use, but its much cheaper than a multi year contract based plan. I only use mine at the lake, so I pay $80 for 5 gb for the month of August, it works well and up to 5 users can tether off the device. Coverage is excellent on Cow, a lot more than I can say for AT&T!
http://www.verizonwireless.com/b2c/m...nd/?page=plans