Need wireless internet access on Macbook Pro for travel in USA [duplicate]

I can say you can use Verizon, they have mifi which you can use it anywhere. You can get a prepaid one at the store. Here is a link of the options http://www.verizonwireless.com/internet-devices/

Also , I know you stated that you will be driving, depending on where you are you have to be sure you will have service as there are many dead zones.

There is plenty of wifi available to the public all over the US, so you might get some free service when you make stops. Places like Panera which is a small coffee shop let you sit and do work. Starbucks and so many other places. I would recommend though if you are in a public wifi to have some kind of vpn service that help you protect your information, never know when being in public area someone might try to steal your information.

Consider buying a prepaid phone with 4G access that allows you to make a wireless hot-spot. If you have an iPad (or your Mac takes Sim cards), you can also buy a prepaid data plan (and again make a wireless hotspot on the iPad)

Multiple providers should offer that (and you get basically free US-phone calls as a bonus)