If Mexico has one rule that explains everything else, it's not in your guidebook. It's not a law. It's a cultural fear that shapes a thousand small decisions a day. Once you see it, you can't unsee it.
Neta is Mexican for truth. It's also Mexican for really, no kidding, for real, I swear to god, you don't say, are you serious, and absolutely. One word. Eight jobs. Said about fourteen times an hour.
No manches literally means 'don't stain.' Mexicans use it to mean 'no way, you're kidding, get out, shut up, are you serious.' One phrase. Eight registers. The polite cousin of a word your grandmother won't approve of.
I lived in 6 cities before Mexico. None of them prepared me for the first six months in the Yucatán. Here's what I wish someone had told me, in the order I figured them out.
Mexicans can spot a gringo from fifty meters. There are ten tells. I have personally exhibited eight of them. Here are all ten, in order of how visible they are.
Pedo literally means 'fart.' In Mexican Spanish it means: problem, situation, fight, party, drunk, vibe, guy, plan, mood, deal, beef, and 'what's up.' One word. Twelve jobs. None of them in your textbook.