San Lucas Quiavini is a community of Zapotec (Otomanguean) speakers in Oaxaca, Mexico. Since the 1970s, the community has seen large-scale migration to Los Angeles, California, where about half the community now resides. Participant observation and interviews conducted over nine years in both locales, with a focus on interactional patterns in the home domain, indicate that parental language ideologies concerning the relationship between language and place of birth, the nature of multilingual acquisition and impact belief--the belief that parents have as to the level of control they can exercise over their children's language choices (De Houwer in "Studies on language acquisition." Mouton de Gruyter, Berlin, 1999), taken together, disfavor the maintenance of the heritage language. In particular, a weak impact belief undermines parents' ability to engage in language interventions in support of San Lucas Quiavini Zapotec. As a result, family-external language intervention factors that promote language shift, such as the school and peer groups, exert great influence. With a substantial number of San Lucas families living in California and their impact on language choices in the home community (Perez Baez in press), family language policy is of great relevance to the survival prospects of San Lucas Quiavini Zapotec not only in diaspora but also in the home community.