Truck stops! (Score 1)

I know you're mainly asking about wireless, but if you're ever in a crunch and need to check your email (especially in them big rectangular states,) almost every truck stop (Transamerica, etc.) has an internet kiosk. Can't do much besides check email, but, it can be useful. Another good place: public libraries (also any and every college campus you come across, as has been mentioned.)
I did this same trip along I-80 this past summer, and it was wonderful. Have fun!
-Jen