Cruz94, again: I think you are reading-too-much into random scars and squiggles.
If you really want to find a cache in Mexico, here's what I'd do: For starters, ditch every single ghost-story legend camp fire story. Forget the conspiracy theory "treasure markers" (me thinks you watched one-too-many episodes of Raiders of Lost Ark movie

) Ditch the squiggles, graffiti, etc.. And instead just get a TM 808 and scan around old ruins there. A TM 808 will find nothing smaller than a soda can sized object. Hence the perfect discriminator against nails, tabs, foil, solo-coins, small junk, etc....
This was the mistake we made when we went for a month to Mexico (Chihuahua and Durango): We had standard machines. Hunted around the ruins of 200+ yr. old homes, and ruins of old churches in the middle of nowhere and in the Sierra Madres. But immediately found that every one of them was RIDDLED with trash. Because, unlike the USA: They have no curbside trash service. So people seem to take their trash and dump it next to the nearest ruin. Or over the side of the nearest cliff, etc.... At first we thought: No problem, we'll just ignore all the small signals (since we were down there for cache-hunting, not fumble fingers solo coins). But it's easier said than done. We found ourselves digging tons of stuff no matter how much we tried to 2nd-guess-target sizes
In retrospect, I wish I'd had a TM-808.
However, I must say, I'm skeptical of the cache stories anyhow. Because as you may know in Mexico, it's very economically divided. So if you had a village/pueblo that's 300 yrs. old, population 5000 or so. Hence 70 or so homes: You'll notice that of that entire population, perhaps only 3 families have most of the wealth in town. Eg.: the governing family. The store-keeper, the mine-owner, etc..... The VAST MAJORITY of the population will be middle and lower class, with very little wealth. So going back in time, 200+ yrs. ago, you'd have to know that the particular ruin you're hunting was the affluent ones of yesteryear. A needle in a hay-stack. And EVEN THEN you're making an assumption that they necessarily hid and never came back for something.
To the degree that .... sure .... caches happen, yet SO TOO could the same be said of the USA or anywhere else . Thus I came to believe that all the treasure stories emanating from Mexico were cultural camp-fire legend ghost-story sillyness. JMHO.