From the Houston Chronicle’s blog from consumer rep Jame Campbell:
Hispanic, Latino – Interchangeable terms for people in the United States who trace their ancestry to Spain or Spanish-speaking countries of Latin America. A Latina is a woman; the plural form for a mixed gender group is Latinos. A Hispanic is correct, not an Hispanic. Keep in mind that these terms describe a person’s ethnicity, not race. See ethnicity, race.
At least that’s what the Houston Chronicle styleguide has.