The price of /all/ food isn't truly kept artificially low when you consider the total effect of laws regarding agriculture in the United States, even if you take into account the illegal immigrant situation. It is true that if all we did was close the border and deport all of the illegals, food prices would probably rise substantially. But if you couple that change with a shift in cultural attitudes regarding Genetically Modified Crops (as well as a few other advances that we've been putting off regarding automation), you can probably recooperate the lost productivity in technological advancements and keep prices relatively stable.
Before there's any outcry about the idea of using GM crops, first note that there is no substantial evidence that GM crops are lacking in vital nutrients but there are studies that indicate GMs and non-GMs are virtually identical in nutritional content
, studies that show that since the introduction of GM crops there's been no detectable link between them and health problems despite the fact that they've been on the market for over 15 years now,
and several of the few studies that seemed to suggest there was a potential problem were bad science.
As you can see, the anti-GM attitude definitely isn't based on science or any other form of reasoning; it probably has more to do with the naturalistic fallacy than anything else.
Of course, the question remains (that actually pertains to the subject matter at hand), will getting these illegal aliens off of the farm employ a significant number of Americans? I suspect, no, it will not. I doubt very many Americans would be eager to uproot themselves from their home to go live in the country and earn a meager living in hard labor which isn't even a year round job (thus is profoundly lacking in job security).
The truth is, illegal aliens don't really do skilled labor. If you're worried about competing with them, get an education. You don't have to go to college necessarily; just learn a trade. That should be something anyone is capable of, and it will pay far better and be much more rewarding besides.
I just don't buy that removing illegal aliens from our workforce will do anything but raise prices (if nothing else is done) on goods and services we buy here. Maybe some good paying jobs would be created in the process, but if prices go up, everyone who's already employed currently and barely making it, or living on a fixed income, gets screwed big time.
p.s. I think we actually have access to the most stable and safe food supply that human beings have ever had. It's easy to think that the opposite is true if you pay attention to headlines, but that's more of a side-effect of living in the information age of paranoia than anything else. I've certainly never seen even a single study or statistic that points to the notion that our food is dangerous. Sure we have health problems, but obesity is not a function of a tainted food supply and what a lot of people often point to--the surfacing of allergies--has actually been shown to be a positive thing in all likelihood (recent studies indicate that there's a lower incidence of cancer in people who have allergies).
If our food supply was so dangerous, or life expectancy would definitely not be as high as it is.