I'll be headed to Oregon-Nevada-Utah- and hopefully Arizona and New Mexico this week. My GF and I take a month (October) off each year. We load up the road bikes and MTB's and just go wherever we happen to feel like.

I'm not up to snuff on the weather in those areas in December, though. Seems like Arizona and New Mexico might be the best bet those months?

I CAN tell you where I have liked the riding a lot. Moab, Gooseberry Mesa, Bend Oregon, Bryce Canyon area, St. George, ElY Nevada area.

Moab, and many other Utah locations, have absolutely stunning scenery. Any direction you look, you can't believe what you are seeing. Especially when you're riding and have the good flow going on and the fantastic scenery, you know you have arrived in a very beautiful state of being. I know that's kinda poetic, but it really is a high feeling.