Bah, you really believe that? where did you get those numbers?
There are several different ways to test it. Look around at the Catholic population of each state and look at its demographics. Also, check polling surveys carefully for ethnic breakdowns of the self-reported Catholic population.
Lastly, take a look around at Hispanic neighborhoods, and note the number of Protestant Churches and the paucity of Mass attendance. The Hispanic (mostly Puerto Rican and Dominican) neighborhood in Philadelphia has around 100,000 Hispanics, but only 30,000 Catholics.
These sort of figures can be found around the country. Thus: "According to a September 2001 archdiocesan report on Hispanic ministry: There were 28,162 registered Catholic Hispanics, about 21 percent of the total number of Hispanics." (http://www.chnonline.org/2002/2002-08-22/special_section17.html)
The numbers are higher (although not that much) among Mexicans, but Mexicans are not all of the Hispanics.
The propaganda the USCCB puts out that the Church is 30-40% Hispanic (implying 2 out of 3 Hispanics is a registered Catholic) is total hogwash. They never back it up with hard numbers, and the implication would read the majority of traditional Catholic population (Irish, German, Italian, French, central European, and Polish) out of the Church.
Perhaps you are confusing Hispanics who are cultural Catholics with those who are actual Catholics. Don't do that. The same confusion among non-Hispanic Catholics would increase the number of Catholics from 65 to 85 million.
Why not compare the registered Catholic population of San Antonio with the number of Hispanics in the Diocese? The results might surprise you.
For example, the Diocese of San Antonio has 640,000 Catholics in 1,900,000 people. There are about 900,000 Hispanics in the Docese by the US Census. If 70% of them are Catholic, as many maintain, that would mean every registered Catholic in San Antonio is Hispanic. Hardly true.