According to the Pew Hispanic Center, a good place to get stats about this issue, half of them enter legally through ports of entry. Since the illegal in "illegal immigrants" is about them crossing the border illegally, it seems to make the designation of "illegal immigrants" even more inaccurate. The PHC prefers to call them "unauthorized". Since this is a pdf file I can't copy and paste so you will have to read for yourselves.

http://pewhispanic.org/files/factsheets/19...

It makes stationing the National Guards at the state borders a PR move by the Bush administration, which will have little effect, just as building a wall will.