I'm going to Mexico City (altitude 7400 feet), and I was considering making pizza there (again). I did this once before without consideration to the altitude, and the dough rose all over the place! It was reminiscent of when Lucy and Ethyl decided to go primitive and bake their own bread.
The Pilsbury site mentions adjustment for baking powder, but does not say anything about yeast. I would be interested in hearing first-hand accounts of baking pizza at high altitudes, but I'll also try to do some more research on my own before I go. I will probably take a few ingredients with me, like some good canned tomatoes, although it is easy to get good fresh tomatoes there. I've generally used Mexican cheese as a sub for Mozzarella, and their string cheese works pretty well, but the cheese may be one of the reasons pizza in Mexico City is a bit off.