I am cheap *ahem* I mean Frugal, and search for the free. I have an IPOD touch, and it uses WiFi as well as my laptop. Most hotels offer FREE wifi. Starbucks, Borders, and many other book stores offer FREE wireless. Many repair shops that fix your car (dealerships included) offer FREE wifi for the waiting customers. When I travel I find its rare to be sitting without some sort of access that is free. Many truck stops now include Free WiFi as well as many reststops with food services.
I hear verizon has great coverage, and its rare that you find yourself without a signal, even in the middle of the woods in a campground. ATT offers nice products, but doesnt cover as much ground as Verizon. Sprint also is spotty in coverage, and while offers good prices, its not worth it if you cant get a signal. Tmobile is the bottom of the ladder. They offer amazing prices, but again, what good is a good price if you cant use the product?
I hope you have fun in your travels.