The Bush administration is doing stuff they'd prefer wasn't made public. That's for sure.
For example, stopping the Border Patrol's interior sweeps.
LOL!
For what its worth...Arabs disguising themselves as Mexicans at the border ..and staying disguised here is extremely difficult. The realities are that a strict sense of discipline is required and even the best trained terrorist would not likely be able to pull it off for very long. Recall all that we have learned about "signals" prior to 9-11...our folks in various agencys are better prepared today.
I do not discount the terrorist efforts but other avenues, such as Canada, seem more plausible to me.