It amazes me what a hot button illegal immigration has become.
Compared to other issues it seems like such a non-issue to me, but I grew up in an environment where most of the orchard pickers (we had an orange grove) and house cleaners were likely undocumented. My family had the attitude that this is the land of oppertunity and why wouldn't they come? And I think that's the point. They are going to come. The human capacity to dream of a better life for their family is not something you can stop or fence out. Putting up more obstacles and increasing enforcement is only going to make them try harder (and at great risk to themselves).
So what is the solution (assuming there's a problem with paying someone below the minimum wage to pick your lettuce.)? Well let's back up and look at a larger picture. There is a huge economic gap in between Mexico and the US (we could include other Central and South American countries, but for simplicity let's just talk about Mexico.) As long as that dichotomy exists, people are going to come no matter what you do. They will find a way - bet on it. I think a real solution would be to improve Mexico's economy. Make life in Mexico more desirable so there isn't the giant incentive to brave El Norte.
Too expensive? Look what we're paying for border enforcement. What if we were to put our money into making Mexico a better, more humane, more hospitable place?
But why should we do such a thing? Well as you are no doubt aware we are 6% of the world's population and consume considerably more that that percentage. I think this is one way to give something back.