Not in an Airstream, but ...
I went on a Copper Canyon caravan with "Tracks To Adventure" out of El Paso, TX with a prior trailer. We spent 5 days on flatcars going over the mountains and past Copper Canyon. I had a great time.
The Mexican people along the way were uniformly friendly and helpful. You do have to guard against pilfering, though. We were advised by the tour folks to take off tire valve caps and other small moveable items that small kids, especially, could remove.
The roads were mostly narrower than here, but in fair condition. There are generally no shoulders on the roads, though, and few places to pull off. You don't want to drop a wheel off the edge, because there are usually dropoffs. The worst thing are the dips where streams cross the road. Wish I could remember what they are called (it has been 10 years). There are always warning signs for the dips and you had darned well better obey them and creep across or you will become airborne and possibly break the suspension of the trailer.
Gas was fairly cheap and of good quality at state-run stations.
Be aware you can't take fruit and vegetables across some state lines, even stuff you just bought at a supermarket. They stripped my fridge at a checkpoint. I figure the guards ate well that night.
John W. Irwin
2005 Classic 28 "Sabre-Dog III"
2013 Silverado 2500HD Duramax/Allison LTZ
WBCCI #9632, TAC TX-10