In my experience, business owners and hiring managers prefer immigrant labor to unskilled domestic labor, because the immigrants work harder and are more reliable.

Also, especially in hard agriculture - often the immigrants make well above minimum wage. At many produce and tobacco fields people are compensated by the amount and quality of what you pick for example. Its obviously seasonal, but while many domestic workers do not even complete the harvest - industrious immigrants can make 30-40 bucks an hour. And they will do it from first to last light. And they totally bust their asses.

You dont see that very often from domestic workers. Ironically, because most american born people who bust their asses that hard have long since been able to move on to more comfortable employment.

In my experience, immigrant labor is actually not favored because its cheaper. But because its more reliable. Obviously this various considerably by situation, occupation, etc

Of course in a down economy, people complain that immigrants are taking up the jobs. Which... is partially true. Going by macro scale averages, your unskilled immigrant labor provides far more value per dollar spent.

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)