Workers in the Shadows By DAVID BROOKS Imagine a person 10 times as determined as you are. Picture a guy who will wade across rivers, brave 120-degree boxcars and face vicious smugglers and murderous vigilantes — all to get a job picking fruit for 10 hours a day. That person is the illegal immigrant. Let's call him Sam. This whole immigration debate is about him, the choices he faces and the way he responds. One thing we know about Sam: he will get here. Between 1986 and 1998, Congress increased the Border Patrol's budget sixfold. Over that time the...