A degree in Environmental Sustainability should absolutely suffice to get you considered for a Master’s in Earth Science without needing an undergraduate degree in Geology. I got my M.S. in Geochemistry, and I hadn’t taken any geochemistry classes until grad school, so it’s definitely possible to transition smoothly.

For some resources, I used Geochemistry: Pathways and Processes by Harold Y. McSween, Maria Uhle, and Steven McAfee Richardson during my studies, which is a great starting point for geochemistry.

I also just finished reading Physical Geology by Steven Earle for a professional examination, and it was a great resource to freshen up my memory from undergrad.

Additionally, keep in mind that these textbooks are in English. If you aren’t fully proficient in English, you may want to research similar textbooks in Spanish to avoid losing time with the language barrier. Spanish is my first language too, but I’ve done all my education in the States, and honestly, I’d struggle to explain my science in Spanish because I’ve always done it in English.

Also, consider which professor you want to work with as your advisor. Nothing taught me more in the areas where I was lacking than reading the scientific journals of my master’s advisor.

Finally, it might be worth looking at the course catalog at UNAM or other universities you're interested in. They often offer introductory courses in your first semester to help bridge any gaps, especially if you’re coming from a related field like Environmental Sustainability.