Barr has some very good points. Effective enforcement probably is better then physical control.

The folks that are coming from Mex. Cent./South America aren't the smartest folks in the world if it came to going through the normal immigration procedures, paperwork, documents, etc, to include passing the citizens test.

My MIL, about fifteen years ago went through the procedure even though she (German) had married an American soldier in the 50's, she wanted to become an American citizen and passed the test etc.

Alot of those sneeking in from the South, aren't too darn far from living in third world situations. I've learned that many who come into this country, are criminals in the country that they left. That's not always the situation, but it's true in many cases.