from wiki but haven't researched the past policies
Conscript Soldiers
Legally, every Mexican man is obligated to a year of servicio militar nacional—SMN (national military service—NMS), but only a few hours of drill or social services on weekends, not true military training. Most conscripts will have received at most only one marksmanship session at a rifle range by the time they have completed their NMS obligation and are not integrated nor operate with regular Army units, and as such despite a national military service the Army is actually a fully professional career force.
The Cartilla
The drafted men attend and participate in weekend sessions that really are a social service in nature, with emphasizes on education, history, physical fitness, and military discipline for one complete year. Afterward, the precartilla (pre-military identity card) is returned to the conscript with an added page certifying his status as having fulfilled his national military service and identifies the military branch, the unit, rank, etc. The document then acquires full status as the Cartilla del Servicio Militar Nacional (Military National Service Identity Card), informally Cartilla; this status is recorded to the National Defense Secretariat files.
This document (Military National Service Identity Card) is an important form of Mexican national identification, and its existence was formerly always requested by private and public employers, however, this identity document has ceased being required for obtaining apassport for international travel.
The other reference given is from War Resistors International
postponement and exemption
Postponement is possible for students, those living abroad, those serving a prison-sentence in the year they turn 18, and those who have to support a family. Postponement is usually allowed for five year periods. [1]
Exemption is possible for medical reasons, for those living abroad and for those living more than 20 kilometers from the training centre boundaries. [1]
recruitment
Call-up for medical examination and registration at the nearest registration centre takes place at the age of 17. Selection of conscripts is by ballot. People picking a white ball get directed to training centres and must undergo military training; people picking a black ball are not enlisted. According to the Mexican government: "Those who obtain a black ball in the draw shall fulfil their military service through availability, without having to present themselves physically for service."
2 Conscientious objection
The right to conscientious objection is not legally recognized.
The Mexican government stated in 1994: "Mexican legislation does not recognize the concept of conscientious objection to military service. For those who are required to perform national military service as one of their obligations as Mexican citizens, it considers that the collective interest in defending the nation must prevail over the private interests of individuals." [2]
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This doesn't answer how the policies were during the 1960s and 1970s. So:
1.How common are these training centers for the 20km to be a valid excuse? I would assume they would be common enough to use 20km radious but maybe someone can enlighten us on this.
2. Would a JW go and pick a ballot? It looks like gambling to me. 50/50 chance of "winning". Would he say, sorry I can't do this because I might pick a white ball? Black ball, service through availability doesn't really go into details from that site.
So the 3rd witness tries to downplay the facts and apolagists go onto imply that we say that all Mexiacan male Jws got their cards during JW years. Just because JWs are known for janitorial work and window washing doesn't make all such. So far, the facts show that Mexicans were allowed to wheasel themselves out of service which Malawi's had to suffer the consequences. Bribe is a bribe doesn't matte rhow much you downplay it. Would Jehovah accept a bribe if Armageddon comes can I squeeze couple dollars in his coffers and get by especially if I live in Mexico?