Just received this info in my monthly miles update from US Air:
Mexico policy change
Due to changes in government regulation, starting on September 13, 2010 we can no longer accept U.S. dollars at any of our ticket counters in Mexico. We can still accept credit cards and Mexican pesos.
Mexico policy change
Due to changes in government regulation, starting on September 13, 2010 we can no longer accept U.S. dollars at any of our ticket counters in Mexico. We can still accept credit cards and Mexican pesos.