First of all, building fences isn't going to stop anyone desperate enough to abandon their entire life for opportunity in the United States. These people aren't just skipping across the border because they want to, they are coming because they have to. They lost their farms when NAFTA shifted the trade balance and made it cheaper to import many traditional crops than to buy locally in Mexico. They can't feed their families.
And then there is the second major component of the immigration debate: do you punish those who are already living in this country -- eleven million of them -- or do you find a way to integrate them into our society? The fact of the matter is that they are already integrated into our society, invisibly, tending our crops and building our houses. We need them as much as they need us, whether we want to admit it or not.
There is no simple solution to the immigration "problem." There are many ways to make it worse. Militarizing the border and creating eleven million new felons, for example. In my opinion, the best ways to deal with the issue are first to make trade fair and work with the governments of these countries to eliminate the conditions that drive their citizens away, and to make it easier for immigrants to become legal residents and continue to play their valuable role in our economy.