On the minus side, I see this happening to name just a few:
Our schools systems will be overwhelmed with new students, many who speak little or no English.
Our welfare systems will be flat broke as many of them learn the benefits that can be so easily obtained.
Once they get their new Social Security cards, they are eligible for the earned income credits from the IRS even if they report no income and pay no taxes. Everyone's taxes will have to go up because of this.
Our healthcare system will be burdeoned with more patients who can't afford the insurance and can't pay for their treatment. But of course we taxpayers will foot the bill for this.
Now for the plus side:
A large percentage of these people are really nice and would make great neighbors.
The farmers and orchard owners will once again get their crops harvested without the need to break the law and hire illegals. Employers will once again be able to fill those jobs that are just too hard or dirty for our own unemployed to even consider. Gone are the days when someone actually had to look for work to qualify for unemployment.
Many of the immigrant children have great minds and are eager to learn. Given the educational opportunities they will someday contribute their new-found skills to society.
Like with most things like this, there are pros and cons. Amnesty is happening and we can't stop it, so it is best to try to make it work well for everyone concerned.