There are some cities in Mexico like Monterrey where life isn't too bad -- if a middle class can almost be achieved there, then why not for more of Mexico (but inside Mexico)?
Actually it would be far better for Mexicans to have Americans come south, bring the US culture into Mexico and build it up. NAFTA isn't helping, but if Americans could build up some of that coastal land and bring in high productive farms, it would be a good thing for Mexico and it's people.
Believe me. Mexico is more Americanized than you think. It is tough to see from here, but if you vacation there, you will see that many things are the same.