Seriously ..
Issue a 5 year green card, and at the 5 yr mark, they have to be able to speak english intelligibly or be deported.
Not the 'king's' english, and not perfectly (heck even I got a *b* in English)
.. just so they can read, comprehend, and act on instructions.
NO HABLA BLAH-BLAH!!
-GE
I don't LIVE in Mexico, so why the mexican signs all over?