You can learn Mexican Sign Language online on Tandem.
Learn Mexican Sign Language on Tandem
Tandem is a free platform with a simple premise: there is probably someone out there who is learning your native language, and whose native language you want to learn. So they put you in touch with them.
When you sign up, Tandem will review your application to make sure their platform remains safe and that the person you get matched with is also a keen language learner.