You're correct that GWB received 40% of the Latino vote in 2004, but that was somewhat of an anomaly. From:

http://latinovotematters.org/stats/

    1980 Jimmy Carter, 56% Ronald Reagan, 35% +21
    1984 Walter Mondale, 61% Ronald Reagan, 37% +24
    1988 Michael Dukakis, 69% George H.W. Bush, 30% +39
    1992 Bill Clinton, 61% George H.W. Bush, 25% +36
    1996 Bill Clinton, 72% Bob Dole, 21% +51
    2000 Al Gore, 62% George W. Bush, 35% +27
    2004 John Kerry, 58% George W. Bush, 40% +18
    2008 Barack Obama, 67% John McCain, 31% +36
    2012 Barack Obama, 71% Mitt Romney, 27% +44

More importantly, the recent trend has been for the Latino vote to be more heavily toward Democrats. Certainly, I agree that Latinos as a whole tend to be conservative, largely due to a Catholic background. However, in current times, Latinos vote more heavily Democratic and by a large margin. Though, less of a margin than African-American voters.