Hitch-Hiking isn't just illegal (nation wide) it is also dangerous. In my youth I would traverse the country doing just that and this was in an era when it was considered somewhat safe and yet, I had a few encounters that weren't pleasant. If you are young and attractive in today's era hitching can land you into a sex slave market, fast! So get yourself a bike and if need be, a trailer for it and bike across country; you'll be far safer.
When it comes to places to hit in order to see magic Vegas is still at the top of the list as is most other major city like Chicago, New York, L.A. and San Francisco but you need cash in most instances though you may find buskers here and there (busking in the U.S. can be a challenge due to local ordinances.) Chasing fairs and festivals is a good thing but you may as well join up with a Carney unit and do it yourself, it's not that difficult though it is some long, hard hours.