When we talk about supply and demand we must remember the illegals are coming from environments where it doesn't take much to have more appeal than home. There are also those who wish us ill so economics is of no interest to them. Like I say, it ain't an easy problem to solve.
The one question that nobody seems to be able to adequately answer in regard to a guest worker program is this: Who or what is going to make the guest workers leave the United States and return to their home countries after their allotted time in the guest worker program has expired?