I just got back from a month-long camping trip from San Francisco to Alaska. In addition to 150 pounds of camping gear, I carried two folding bikes in a Cessna 172. I removed the rear seats to allow for more cargo space.

I own a Schwinn 20-inch bike and a Dahon Vitesse bike. The Dahon fits nicely in the baggage compartment, though I had to remove its luggage rack to get it through the baggage door. The Schwinn takes some maneuvering, but I was able to load it through the front doors.

It was a little unpleasant to unpack and repack the airplane -- it took about an hour each time, given how much gear I had. But oh man, the folding bikes were invaluable.

If your on-the-ground distances are smaller, and the roads are paved well, I would consider carrying a Razor scooter instead of a folding bike. It doesn't travel as fast, and there's no shock absorbers so your wrists will get tired, but it's about the easiest and most portable ground transportation I own.