That is an unbelievable growth rate, and it's inevitable that they will have to expand their living space. It's probably the biggest dilemma the US will ever face in it's lifetime as a nation. It's obvious that we are being used as a safety valve for Mexico's elite, and politicians here who accept and encourage it. The future does not portend well for future Americans if what's happening isn't halted completely, and the border closed. And Mexico is going to have to slow down their birth rate. Like it or not, we're stuck with this nation, and we'll have do something to help it. Anything however but the status-quo.
I think the Mexican leadership regards the high birth rate as an asset. I believe that it serves their purpose: They know that desperation will drive people north into gringolandia. Which of course means, eventually, political power here, and cash remittances to there. They are DESPERATE to keep their people HERE. It is EXACTLY what they want. ALL of their efforts are aimed at that, which is why immigration supposedly being off the table at the summit has to be a big blow to them.
It postpones the long term plan for population driven political hegemony in the U.S.
So I don't see them trying to solve this anytime soon. In fact, I'm sure that they will encourage more big families, and then literally drive them over the border, where their fellow travelers and consular officials will work night and day to keep them here.
Tancredo said in a quote the other day that he thought it "bizarre" that the president of another country would be trying so hard to get rid of his own people. But it's not bizarre from their point of view (the Mexican leadership). It's quite rational. Helps them achieve their goal.