I forgot to mention traffic in Colorado. It can be bad, especially in the summer, and ski season too for that matter. Anywhere close to the big cities on the eastern side (Denver, Colorado Springs, Fort Collins and Pueblo) can remind you of L.A. or Houston traffic at times. US-24 west of Colorado Springs is stop and go for miles on weekends. I-70 west of Denver can be bumper to bumper all the way to the continental divide.

The west side of the state is much better. You'll still run into motor homes holding up a dozen cars but at least you're moving, and can always stop and take pictures. The main roads (US-550, US-50, US-24, US-40 and I-70) tend to be the worst in the west. The state roads like CO-145 and CO-141 will be better.

And there's also CO-65 over the Grand Mesa. That ride is spectacular and very lightly travelled.