I want to recommend an article from yesterday's New York Times, "Cost of Illegal Immigration May Be Less Than Meets the Eye." It appears that the hiring of undocumented workers doesn't drag down the wages of native-born high school dropouts nearly as much as most people think -- primarily because business owners who employ illegal aliens choose to keep their business operations in America or expand their operations in America more than they would otherwise, which has a positive effect on the local labor market. As you can see from this chart, states with a lot of illegal immigrants are absolutely not the states with the worst wages for native-born high school dropouts.
Look, this is all about business. Business owners are blackmailing us: Let us keep hiring illegals or we'll take our operations to Mexico, or at least cut back here; let us keep hiring illegals or you're not going to like what happens to the prices we charge. And we accept that -- as is noted in "Going After Migrants, but Not Employers," also from yesterday's Times, legislators, including some who are now talking about getting tough on immigration, fight for employers in their districts when the those businesses are facing INS penalties. And there have been far fewer INS investigations of businesses in recent years -- see this chart.
If the anti-immigrant zealots really don't like the status quo, if they're really going to insist that the flow of immigrants should be not managed but stopped, than they have to take on influential capitalists, rather than directing all of their anger at illegal immigrants ("Speak English!"). They'd have to demand that influential corporations be punished for hiring illegals -- in ways that really hurt -- and demand limits on the ability of these corporations to take their operations overseas at will (or mount effective buy-American boycotts of globalizing companies). But they're not going to do any of that -- obviously, it's much easier to direct anger at a group of Mexicans at a day-labor pickup site.