My take on the "Immigration Issue".
Hmmm...so it seems that 10% of Mexico's population has migrated north of the border to work and/or live, on the good side of a 10:1 exchange rate. It's mostly "work", as far as I can tell. [Obviously, undocumented immigrants have arrived from all other nations in the Western Hemisphere and some from the East, but Mexicans comprise the bulk of undocumented immigrants due to their locale, and serve as the public face of the issue.]

Instead of Paul Revere seeing lamps in the tower and riding across the country to call out a warning, the Mexicans (and others) have already arrived, by land, air, and sea, and have settled all over the U.S. As expected, very little concrete discussion has taken place, as several vested interests play this development for political gain. From what I can tell..

• Midwestern 'conservative' leadership (aka taliban) equate brown people with Communism, and would probably like to jail anyone (legitimate or not) daring to cross the border, but will have to settle for those that don't have paperwork. I think the characterization of 'illegals' has come from this segment.
• Southern 'conservative' leadership (a mix of plantation class and taliban) find the flood of cheap immigrants to be what slavery should have been -- a pool of transient labor that and goes "somewhere else" after their job is done, leaving the permanent residents to run things, "as God intended". Various official acceptance positions come from this segment, as well as President Bush's deflationary remarks to the effect of "we can't deport them all". Note this sentiment fades the further west one gets, with Southwest being somewhat more practical, as they form the main border in question.
• The Mexican leadership appear to be what the U.S. Southern leadership wanted to be: a truly landed class, whose control applies at a national level, vs. a local or regional level. They seem to be happy to offload peasants and peasant overhead onto the U.S., and happier to accept the resulting economic leverage against their northern neighbors. If they ever had their cumulative act together, the exchange rate would be much tighter.
• The Communists, in their socialist "bat form", assume the classic position of parlaying bad incumbent policy into political gain. This time, they have the advantage of using a culture difference, and two disinterested, illegitimate incumbent parties to play against. They use the wave of brown people as a tool to instigate worse policy and unrest, and use the inches given from those actions to claim miles of political gain and control.
• As for the immigrants themselves? Making one's annual pay in a few weeks or months is a fine prospect, so it's a matter of placing themselves and/or their families where work is plentiful, biding their time until then, and/or raising kids in the U.S.A.