I do think they should tighten the borders, and make the flow more organized and legal, but I don't think anyone should have to leave, felons excluded.
Those 10-12M immigrants make up much of the foundation of the economy. Without em, nearly all of our wages would go down, as ppl doing menial labor would suddenly be paid $20 an hour instead of 8, and they'd demand benefits, etc. Watch the price of a lot of things you love go up, and the wage you bring home go down, as employers have to put more resources in lower jobs. It really would even out the wage discrepencies a bit, but it would suck for most of us!
But yeah, you should be able to beat - with a tire iron - anyone who wrecks your car and leaves the scene cause they're illegal.