I think that sounds like a lot of fun! I googled it and some of the pictures on the site look crazy.That's definitely a good deal of climbing, especially on dirt but at least the starting altitude isn't too bad. I did a little mountain biking in San Pedro de Atacama in December and the altitude killed me (not to mention the heat!)
Another great ride is the so-called (<-and with good reason!) World's Most Dangerous Road out of La Paz, though the road sees a lot less traffic now that an alternate route has been built. Gravity Assisted Mountain Biking (www.gravitybolivia.com) is great. They do a lot of other rides as well, all MTB.
I have this crazy idea of cycling the length of Chile some day. I was reading the blog of a guy that did the same and saw the entry where he approached the Argentine border at Paso los Libertadores. Crazy!!!
Anyhow, I hope you do give it a shot and post pictures!
Anne