Why would they?
They are here illegally, get rid of them.
BTW we got rid of 1/4 of the population after 1789, for staying loyal to the king, you really don't thing we can move out 1/10 of the population.
The truly sad thing is that Mexico has no reason not to be quite prosperous. No reason other than the 80 + year rule of the PRI.
They have:
-two coasts
-fertile land
-oil
-uranium
-easy access to the United states AND South America.
-some infrastructure and a strong religious faith.
One thing that bothers me when I see so many aliens is that I bet a lot of these folks ARE the hard working risk takers(yes, there are some criminal scum, too, of course). They should be the ones starting businesses and creating jobs in Mexico. The real question should be how to help the Mexicans perform their own econoimic miracle so that there aren't so many coming up here in the first place. Most of the Mexican nationals I've ran into had better manners and morals than most elected Democratic officials:-)