That still doesn't explain why he couldn't enter the country legally. He's honest and hard working, so there shouldn't be an issue. By entering legally, he'd have an easier time to probably do more for his family back in Mexico. That's my opinion of course.....
Like on South Park when people came from the future because it was crappy and no work was to be found. They all found that making the future a better place to live, they solved both their problems. IMO, that was a very good point to what issue they were hinting at.
Now, if only President Fox would try to help his own people rather than expect America to

He's a big part of this problem!