Everyone born in Mexico is considered a Mexican National, and foreigners who have resided in Mexico for (typically) 5+ years, and fulfil a number of requirements, can obtain Mexican Nationality. Mexican Nationals can after age 18 become Mexican Citizens, which confers additional rights, however Citizenship is not required to obtain passports, visas for other countries, and travel internationally.
Most government websites I've seen regarding travel permissions for Mexicans refer to Mexican Nationals (the US Trusted Traveler Program, for example).
A such, I believe the tag mexican-citizens should be renamed to mexican-nationals to fully include all Mexicans.