That’s not what I read from the Pew Religion and Public Life survey. They say the number of Catholics has been dropping for decades, and that at this point those coming from Mexico to the US are 70% Catholic. But your stats may vary. Your source?
The Pew I see gives 70% of foreign born Hispanics as currently Catholic, not as having been so the day they fled Mexico.
Many Mexicans leave the Catholic denomination after escaping Mexico.
The figure of 94% of Mexican immigrants having been baptized Catholic, is from the NHCLC.