Teachers' language ideologies shape their classroom language policy-making, which in turn shapes students' opportunities to learn. Attention to language ideologies is therefore critical for teacher educators who seek to support pre- and in-service teachers in becoming pro-multilingual policymakers. This mixed methods, survey-based study explores the language ideologies and hypothetical policy-making of 134 pre- and in-service teachers at a large public university in Arizona. It employs decision tree models to examine connections between participants' demographics, their language ideologies, and their hypothetical policymaking around Spanish-English dual-language bilingual education (DLBE). Findings show intersections between current and future educators': (a) contextualized experiences, (b) ability to discuss DLBE accurately (without misunderstandings), and (c) ability to engage concretely with details of hypothetical policy making around DLBE. The study offers a unique vantage point from which to consider how pre- and in-service teacher education can inform teachers' accurate understandings of DLBE/multilingualism, language ideological stances, and stances toward linguistic diversity.