Mateo hails from Tucson, Arizona. As an undergraduate, he was an officer and internship director for the organization, Fostering and Achieving Cultural Equity and Sensitivity in the Healthcare Field. Mateo has worked with various nonprofit organizations, including environmental groups, interfaith agencies, and refugee initiatives. Most recently, he worked as a habilitation provider for children with autism and cerebral palsy. Mateo graduated from the University of Arizona with a Bachelor of Science in microbiology and a Bachelor of Arts in Spanish translation and interpretation. He is a Davis-Putter Scholar for his work in LGBT migrant rights and for documenting cases of migrant abuse on the U.S.-Mexico border.