I live in Florida, where we have a huge agriculture industry and a lot of illegal workers, many of whom are Latinos. In fact, the lab I work in has ties to the citrus industry. I've participated in harvests of experiments and have yet to see a non-Latino working on a picking crew. It's ass-busting work - climbing up and down rickety ladders with a sack of heavy fruit. Pickers are paid by the volume of fruit they pick, so they work as quickly as they can. The weather can be anyway from 50-80 degrees and the pickers generally work from 6 or 7 am to 4 or 5 pm. It's a long day. The pickers also dress in gloves, long pants and long sleeves to help reduce the unavoidable scratches - many varieties of citrus have nasty thorns. And a good number of them are illegals. One time we worked with a super nice crew and I had time to talk with the guy in charge. He's only ever had 1 white guy work for him and that guy only lasted a day. So no, I just don't see these folks taking jobs away from Americans. A few years back the INS cracked down on picking crews. The pickers that weren't caught were afraid to work for fear they'd be picked up, too. The grove owners did a lot of worrying that year with the shortage of pickers. It's not like the Americans who were having their jobs taken away were now rushing in to fill the vacancies.
So why is it such a problem to allow these folks to live and work legally here? They're already here and working hard. Why not allow them legitimacy, security and protection from ruthless employers who may otherwise try to take advantage of them?
I found an interesting link: