That's exactly what's happening here in this country with illegals........a significant % cannot speak English (and won't learn it), they have no skills and exist only because of overly generous (and idiotic) welfare system........in effect, they're mission is to colonize.......not assimilate.
Our laws need to be enforced, and no one should be here illegally, but if we are going to fix this problem we can't get hysterical about their real motivations for coming here. 99% of it is economic. Some DO come for the welfare, but most come for labor, which (based on where they are coming from) IS welfare.
And studies I've seen say that legal or illegal, Hispanics learn English in a much shorter generational time than Germans and Swedes learned English in the 19th century. Again, it doesn't take away from the fact that they are here illegally, but the "La Raza" kind of emphasis by immigration reformers will only hurt the cause, especially if it's not true.