Mexican authorities must keep track of every single person in the country:
Federal, local and municipal police must cooperate with federal immigration authorities upon request, i.e., to assist in the arrests of illegal immigrants. (Article 73)
A National Population Registry keeps track of every single individual who comprises the population of the country, and verifies each individuals identity. (Articles 85 and 86)
A national Catalog of Foreigners tracks foreign tourists and immigrants (Article 87), and assigns each individual with a unique tracking number (Article 91).
Do they keep track of those who end up here?