Jason, can I save you a ton of time ? Mexico superstition lore is jam-packed with "sure-fire-treasures" everywhere. Everyone down there is certain that treasures most certainly lurk in every cave, ruin, etc.... Conquistadors, pancho villa, blah blah blah . And they're all silly embellished legend.
Where I live in central coast CA, is lots of agriculture. As a result, a lot of emigrant labor comes here for jobs. So I have met scores of folks born there, and moved up here. And ... yup .... they've all got treasure stories like yours "if only we had a metal detector that could detect 2 to 3 meters deep!".
At first I was always spell-bound by the stories. Each one packed with "iron-clad proof". So eventually I joined up with an employee friend , who took me deep into the mountains of the Sierra madres. Little mountain towns that were 300+ years old , where the Spanish had mined gold. People living in old adobe homes that were hundreds of years old. Churches from the 1700 & 1800s, etc... But when we got there, and I started inquiring more deeply about the treasure leads we were there to pursue, turns out they all fall apart. They were all of the sort like "he said that she said that they saw, that he said, that ....... ", well, you get the picture. Supposed treasures that were found already, when you went to try to interview the person, well .... it turns out they didn't exactly see it themselves, but they knew the person who did. So you go to try to track down THAT person. And ... well , it turns out they too didn't exactly see the treasure. But they knew someone else who did! And so on and so forth, till you finally realize THERE WAS NO TREASURE. Yet when it gets told over and over, before you know it, it's "200 bars of gold" blah blah blah
So I have come to conclude that all the mexican treasure lore, is of the same sort as the Philippine yamashito type stuff. Fun campfire stories, but total bologna. I know you won't believe what I'm telling you, because the lore is that deep. But ... I tried.
