My brother's wife (fiance at the time) immigrated from Canada. It cost thousands of dollars for her to get here, transfer everything, get a Social Security Number, she and my brother had to provide proof of their relationship (letters, emails, text messages, etc) and a multitude of paperwork and interviews with both governments. Then she was not allowed to see my brother for six months while all the documentation went through, and once she got here, they had 6 months to get married or she'd be deported.
On the other side of the U.S., Mexicans enter illegally. Can't say I blame them.
Anyhow, I say if illegal immigrants are productive in society, we can work with them to grant them citizenship. If not, try to get them to be productive or say "bye bye".
Also work to tone down the excessiveness of the legal immigration process. But definitely keep that border fence up and running.