If you're going to get a folder, the smallest wheel size should be about 20 inches minimal. I always prefer a larger wheel bike if you can manage it. Do not get a 16' inch wheel folding bike unless you plan on using it in conjunction with your boat or airplane where space is at a premium. A small folding bike with 16' inch wheels inefficient, unstable and provides very rough ride.

If you're going to make a compromise, a folding bike with a 20' inch wheel is the way to go. Since your from Minnesota, I would stay away from Birdy or Brompton as these bikes are way overpriced in the U.S. for what you're getting as they have to be imported. Furthermore, support and special parts for these bikes are not to be found in your local bike shop.

The only folding bikes companies I can recomment are those from Dahon and Bike Friday. If you have the money, go for the Friday.