Why the title?
It was only used once in the movie, and it had no significance.
shareI think the title is designed to tease as it's a line said once (by Julio) towards the end and it's hard to know if what he says is true or not. However, given Luisa is an older woman and related (by marriage) to Diego then the title has resonance in relation to her too.
It has further significance in terms of the disintegration of Julio and Tenoch's friendship because Julio trumps Tenoch in the betrayal stakes if he did beep Tenoch's mother.
Keep silent unless what you are going to say is more important than silence.share
When I first watched the bar scene, I thought that Julio's statement ("y tu mama tambien") was simply adolescent joshing. But having watched it multiple times now, I believe that he was telling the truth, for 3 reasons: First, he gives a specific time when it happened (can anybody give a better translation of what he is saying when he refers to cleaning or cleansing?); second, in the bar scene that night, they have created a general "amnesty" for anything that anyone wants to confess. Luisa started it by confessing how she knew her husband was cheating. Then she confesses that despite all her earlier anger, she's really glad she met the guys, and they are "cool dudes." After that, the confessions get more and more intimate, culminating with "y tu mama tambien." Third, Luisa believes him, Julio never says it's a joke, and the boys follow it up by toasting "all mothers." However, once sober, that confession might not go over so well.
shareA "cleansing" refers to a shamanistic spiritual cleansing ritual (in Spanish "una limpia"). Tenoch's mother performed one onto Julio, and later they had sex if I remember correctly.
Context: After confessing to Tenchoch that he had sex with his mother, Tenoch says something like "Oh really? When?" and Julio says "For real, dude, the day she did a cleansing on me", or something along those lines. Pictures of cleansing rituals:
http://bunkerpop.mx/wp-content/uploads/2014/01/enhanced-buzz-4459-1382756462-4.jpg
http://static.quien.com/media/2011/03/19/boselimpia.jpg