I agree that the character of the individual will ultimately decide the quality of citizen that a person becomes, and that legal immigrants that come here to exploit any loopholes in welfare and social services are not good choices. I don't know exact statistics, but I suspect that they are a small minority among immigrants that choose the legal route, however.
Also, I agree that there should never be more than 5 or 10% total foreign born immigrants in this country at any one time ... we are fragmenting and balkanizing our country every day, so numbers have to be controlled to allow for assimilation and accomodation.
Under no circumstances should illegals be rewarded with amnesty. In fact, I am all for ammending the constitution such that persons born in this country to illegal aliens do not automatically become citizens. And if you are caught as an illegal alien, you can never come back. Period.
One way to make sure we're not getting the freeloaders would be to deny any sort of welfare program --WIC, food stamps, SSI, Medicaid --to immigrants for 20 years after their arrival. If they haven't got the work habits or skills to make it here then back they go.
Where I live there are so many who manage to find the loopholes though and end up on government assistance and in the projects that I can see where it could be far more important to end the practice of anchor babies and certain family reunifications than it would be for the INS to hunt down the guy out there working in the fields from 3am to 7pm at least earning any cash he gets. SSI is one big program that is very easily abused.