Blown among whom, the Mexicans they're crossing with? I think the point is that they're joining the stream and hoping to be among the 90% who never come into contact with a Border Patrol agent. And if they do, hope to "pass," getting shipped back across the order to try again. If they know enough Spanish to understand what's said to them, they could presumably just present their documents and refuse to speak. The BP might just shove them back across the border without knowing they weren't really Hispanic.
Exactly......