Considering my limited European and British driving experience, I'm happy to report we have no round abouts...Almost all of the roads between cities are Interstate highways, meaning at least two lanes and as many as 5 going your direction, well separated from the opposing traffic. One has to keep an eye out for the signs indicating exits, but they usually give good advance notice as well as multiple notices. A good investment would be to purchase or rent a GPS navigatior... seems the Tom-Tom is quite reliable for up-to-date data bases.
Unfortunately, especially considering the 12 seat bus is the fact that our gasoline (your petrol) prices have started climbing unmercilessly. Right now the national average is about $3.50 per U.S. gallon. I realize you Brits have been paying more than that for a long time, but it's quite a shock to our system. It's estimated that it could go to $4.00 by the end of the summer. Be sure to select the lower octane ratings (87) for savings... it will do just as well since almost all have about 10% ethanol.
Welcome to the U.S., by the way!