It is fairly well understood by anyone living in statistical reality that illegal immigration is fueled by economics. Since the United States does not enforce it's immigration laws, illegal labor could earn more money in the United States and employers loved the cheaper wages, no workman's comp, no unemployment benefits and no taxes.
So, now that the economy is falling apart illegal labor is going home.
Will this help the unemployment statistics and wage levels for U.S. legal unskilled labor? It's yet to be seen but at least the economic realities of what causes massive influxes of illegal workers is being made quite clear for the majority. Of course the multi-billion dollar underground drug economy is a whole other ball game.
It's about earning money any way one can and trying to earn the most money one can. It's about how regional economies when collapsed will cause dramatic, massive influxes in labor supply to other nations unless immigration laws are enforced and domestic economies craft policies to create strong regional middle classes, both for strong societies and for stabilization of labor markets.