Well that seems obvious to you, me, and anyone else willing to look at actual data and facts regarding voting patterns of immigrants, but it apparently does not register with people like Giuliani, President Bush, Senator McCain, Michael Barone, Fred Barnes, and a whole host of other liberal-on-immigration Republicans. They have actually bought into the nonsense that says immigrants are ‘natural Republicans’ who would vote that way if only certain bad guys in the party would stop being so mean!
The truth, of course, is that for every factor by which Hispanics may be naturally inclined to vote Republican, there are at least as many other factors pushing them towards the Democrats, and those pro-Dem dynamics are obviously stronger than the pro-GOP ones.
The only chance the GOP would have with Hispanics (short of completely copying the Democrats) would be in an environment of much reduced immigration, where assimilation will take a much stronger and faster hold. I am amazed that there are conservatives who think that the GOP can actually win (or break-even) among latinos while the inflow continues to be so large. High levels of immigration (legal or illegal) strengthens pretty much every dynamic that makes them lean Democratic in the first place.
You are assuming that legal immigrants will be from Mexico and points south. This is not necessarily the case if the US stops illegal immigration and operates a skills based immigration system and makes sure that legal immigrants come from around the world so that you don’t have half the population from one fairly dysfunctional nation.
This in effect was the reponse in the 1920s to World War II after the population became alarmed at the flood of (legal) immigrants at the turn of the century.