Can't remember the budget but things we did:
Hired a mustang convertible in LA to drive to Santa Barbara (about 140 miles on the clock when we got it)
only one speeding fine for the whole trip, I think I've gotten away with that
Internal airfares were Virgin America, LCC but excellent food & wi-fi on board. Limited network but they happened to be going where we're going. DC to LA was $249ish. Velocity FF & status credits
The only thing we found a bit expensive was hotels, if you book that from AUS seems to be a bit cheaper.
Renting cars is a pain in the arse over there, ends up being around twice the quoted price with taxes & fees especially in California. Still reasonable price though. Don't fall for the up selling though. Renting a GPS is really expensive, DON'T, buy a cheaply from Walmart & keep it for the next time you go.