I don't travel as much as I used to (domestically), but I've only been in one situation where I could not find free wifi nearby. It was a hotel that had free wifi to the third floor. Unfortunately I was on the 5th.

In Oklahoma at least, many restaurants offer it for free as well as libraries, shopping malls and most hotels. I'm finding that fewer and fewer establishments are charging for access. Many fast food chains offer it although they don't really advertise it well.

Then there are the unsecured wifi networks that work in a pinch. I figure if they leave it open, it's available to use. I try and not use it unless I just happen to be out of cellular data coverage (rare) and I need a google map or something like that.