I live at sea level and do a fair amount of riding at altitude, in the Sierras. (The Death Ride which I have done twice ranges from 5,000 - 9,000 feet - its 130 miles with about 14,000 feet of climbing total, and we've also ridden a lot in Yosemite up to Tioga Pass and Glacier Point, about 10,000 feet).

As mentioned, it would be helpful to get there a bit early to acclimate. Also, everyone responds differently to elevation and if you have no experience with it, it would be nice to know what to expect from your body. I find I breathe more, sometimes I don't feel that I want to sustain an anaerobic effort level as long as I would usually, and sometimes the climbing slows a bit, but otherwise I don't feel any ill effects. Most of my problems with altitude happen the first day I am there unpacking the car!

Good luck.