This research investigated how a Critical Sociocultural Linguistics Literacy (CriSoLL) approach to authentic materials supports student literacy in a mixed Spanish heritage language (SHL) and additional language (L2) Spanish intermediate course at the university level. Using a qualitative approach (Cho, 2018; Esposito & Evans-Winters, 2021) and action research methods (Kemmis et al., 2014; Pine, 2008) exploring the attitudinal stances of students, the investigation examined a CriSoLL theoretical and pedagogical approach to authentic materials, using my own and already existent CriSoLL-based content of authentic materials designed to focus on Spanish in Southern California. Data was collected using (a) a language background questionnaire, (b) a one-on-one semi-structured interview with students, (c) an analysis of selected written and oral student assignments and assessments, (d) surveys at the beginning and end of the quarter, and (e) a researcher journal. Results showed that students became more critically aware of local stylistic language practices and their symbolic meaning, thus reporting a greater sense of pride and agency in their linguistic choices. By analyzing examples of U.S. Spanish and language ideologies learned in class, students' responses to the assignments and surveys showed an increased critical literacy development of the linguistic dynamics of their local environments, which inspired students to want to take action towards sociolinguistic justice in their local communities. This research brings attention to the types of raciolinguistic ideologies involved in what is considered "authentic" language in Spanish language instruction and considers alternative approaches to critical language instruction inspired by notions of Indigenous relationality (Wilson, 2008). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]