Foreign workers do not pay into SS since they do not receive SS benefits. (There maybe some exceptions but this is the general rule.) The only way a foreign worker would pay into SS system is if they were pretending to be an American worker. I do believe it is a crime to forge US documents, if not please let me know, I'd like to start copying twenty dollar bills right away.
What is happening is Bush is going to put millions of illegals into the SS system so that they can collect SS benefits back in Mexico, and you and I will have to pay for it.