Can I save you some time? "Gold caches" and "treasure" stories in Mexico, are a dime a dozen. They're all superstition, in my opinion. Everyone down there is utterly convinced there's treasures in every cave, every backyard of all old houses, in the walls of every old ruin, etc... And when they spin the stories for you, of course they're all iron-clad. Because someone told someone, who told someone, who told someone, who saw fire coming out of the ground, or the virgin mary told them in a dream, or they saw smoke in a vision, blah blah blah.
I too heard all the compelling stories, complete with the additional evidence of other treasures found nearby. So "if only we had a metal detector that went XX feet deep, we too could find treasures in my town". So off I went, travelling all over Mexico chasing stories with my host friend. And when we arrive way back in the boonies at teensy little villages that date to the 1600 and 1700's, all we find is junk, and a few individual coins around ruins. So I asked to see some of the coins, that came from the already-recovered treasures he told me about, before we left the USA. So we go over to distant relative's houses, who had told him the stories. And as it turns out, they *didn't* actually *see* the treasure or coins, but had heard about it from a reliable friend. So we go to THAT person, and ask where the coins are today. Well you guessed it: they too hadn't actually seen it, but had heard about if from a friend, who heard if from their friend, etc.
You see how it works? And no matter how many times the story gets passed down and embellished, it's utterly taken as fact. And don't dare question them, or call it "superstition", lest you offend their machismo. Besides, if your detector doesn't give a signal in a cave, it NEVER means a treasure isn't there. It merely means the machine doesn't go deep enough.
It was almost comical after a month down there.
Sorry to be a killjoy. I'm sure there's been some recoveries. And so too has there been recoveries up here in the USA too. Fun place to visit, but I have my doubts about any treasure stories I hear from immigrants who come here. If you must go and chase stories, have a 2-box machine that will simply not hear anything smaller than a soda can sized object. Because there is trash EVERYWHERE in the remote towns and villages. Because unlike here, where we all have curbside trash service, down there, they just bury their trash in the yard (or in burn pits, etc...), or take it out to the nearest cliff and dump it over, or dump it by the nearest ruins, etc... We found modern trash (and lots of it) even at the most remote ruins we came too, as if any old wall becomes a good place to "dump the trash". By using a 2-box machine, at least you won't spend countless days and weeks digging small stuff.
My host knew first-hand, of the very things he was telling me. It was his immediate relatives, blah blah blah. And no one could dissuade me from going, as the stories were just too compelling. I too had images of all the gold coins I was going to find. 
