Lived in Yucaipa back in the 80's when the migrant workers from Mexico were kept from coming into Orange County to pick the strawberries. Employment wasn't all that great as a lot of people were complaining about not finding work. The growers put out ads, went to the empoyments offices, etc., looking for workers to pick the strawberries. A lot rotted because the Anglo's couldn't take the heat of the fields and quit right away.
I was born and raised in Ohio where we had migrant workers from Mexico all during the harvest for tomatoes, beans, etc. that had to be picked by hand. I didn't think anything about it -- they came for harvest and went back to Mexico after the harvest. Were they here illegally -- I have absolutely no idea but without them, the harvest would not have happened and the produce would have rotted.