First of all, NO. The 10 million or so who came to California, are mostly Indian in appearance and background. They don't resemble white people in the least, with a few very rare exceptions.
Secondly, even if they were all blond Castilians, the fact is that Mexicans and Central Americans are NOT ASSIMILATING to the historic Anglo-Puritan culture in the way that prior waves of immigrants (Irish, Italians, Swedes, Polish, etc) did.
In fact they actively resist assimilating, for the most part, and are intent instead on forming another internal oppositional anti-culture. As if we needed another... damn those slaveowners to hell for creating the first one...
So, no, magically pronouncing millions of bronze Aztecs as "white", won't change anything. Culture is the issue, not blood, as this post so clearly illustrates:
http://www.freerepublic.com/focus/f-religion/2488099/posts
Mexicans are not the only “Hispanics” in the country. The Census numbers are not taking into consideration culture, they are counting numbers of people according to how they self-identify. I wasn’t actually referring to blond Castilians. Genetically, these people are Caucasian. Look at Marco Rubio (Cuban descent) and tell me that he is not White.