Alright, I won't "just" say to build a fence. But building a good fence like the one the Israelis have will go a long way towards getting this problem under control. Nor would it come close to breaking the budget. And we need to completely unleash state and local governments in acting against illegals. The New Hampshire authorities recently tried to prosecute some illegals for trespassing when they were caught traveling along the state's highways, and a court struck down the attempt on the grounds that New Hampshire was allegedly interfering with Congress's authority. Congress could remedy that instantly by passing a law making it explicitly clear that states may act against illegals in whatever way they see fit, limited only by the Constitution itself.
And above all, our government needs to speak with a united voice (or as close to it as possible) that there is absolutely no possible way that illegal aliens will be able to benefit from a guest-worker program or any other kind of legal status unless they first go back to their home countries and wait in line the right way. Holding out that possibility for them, as Bush keeps trying to do, only encourages more illegal entry.