By older Hispanics, I was referring to those who came in the period 1590-1900 or thereabouts and settled in the southwest.
Many others came from Mexico, esp. northern Mexico, mostly after 1900. The border was not a barrier, a typical example is Lydia Mendoza and her family, Tejano musicians who worked and lived on both sides of the border.

The Census provides a few figures-
Of the 39 million Latinos in the U. S., 67% are of Mexican origin. Mexican immigrants account for 38% of the Mexican origin population. About 1/5 have gone through the naturalization process.
77% of farm workers in the United States are Mexican immigrants. Many others are in service and construction industries.

The populations of several of the large farming-cattle-fruit counties in south Texas are predominantly Mexican immigrant. San Antonio is 41% Mexican immigrant, 16% other Hispanic (older inhabitants, etc.), El Paso is 64% Mexican immigrant (total 77% Latino).

Over 4 million of the citizens of California are Mexican immigrants.
Some 2.5 million of the citizens of Texas are Mexican immigrants.
Most of these citizens received their papers on length of residence, children born to Mexican parents working in the U. S. (1/2 of all Latino children in the U. S. have one parent who is a Mexican immigrant), service in the U. S. armed forces (for many years a route to citizenship for 'illegal' immigrants- no formal immigration procedure required).

In 1986, 2 million Mexican immigrants were 'legalized.' Currently, it is estimated that the undocumented population from Mexico is 5.3 million (2002). A pathway to citizenship for these immigrants should be provided by Congress.

They have proved to be good citizens. 44% of Mexican immigrants are home owners. They pay their taxes. They respect their Mexican roots, speak Spanish at home, celebrate Cinco de Mayo (defeat of the French army, 5 May 1862 by Texas-born General Zaragoza. Incidentally, this kept the French occupied and prevented them from providing supplies to Confederate forces during the Civil War). We should add it to our American holidays.