It seems like the sort of thing he'd do - despite his mannered, butlerly exterior, Alfred has always struck me as the sort of person who's not afraid to dive in with gusto and get his hands dirty. A road trip would seem to be just the sort of thing he'd try - plus, it might be just as much for his own benefit as Bruce's; as a native of the UK who (if I remember correctly) came directly over to Gotham and a job as a faithful servant to the Waynes, he probably hadn't had much of a chance to see any of the US.