Philo-Beddoe and SuperDave : You've given me a link/post that's over 100 pages long !
You'd need to direct me to a specific individual(s) post(s) that you want me to specifically look at.
I've got over 100 reales, and a few hundred phoenix buttons from CA sites. And have hunted many many mission era (ie: "el camino real") sites. And my mentor, before me, was hitting mission type sites (and even several of the mission!) back in the 1970s and '80s, when you could get away with it (simply knock on the door, and the priest on duty could say "sure"). I have hunted 2 of them in that fashion myself, via some credentials I hold (d/t they're private, not public property). The only reason I say all this, is to preface, to show you I have a bit of ... uh ... ability to speak on the subject of pre-CA-statehood CA (ie.: Spanish and Mexican period sites).
So with all that said, and glancing at the links title, and browsing through a bit : I'm going to have to say I put zero stock in "vaults", and "marker clues" (cryptograms, etc....).
As for "vaults" (ie.: big treasures, gold/silver of mission era origin) I don't believe it for a minute. The missions here were at the remotest ends of the earth, for that time period (no refined metals, no manufactured goods, etc...). So when trade and supply ships DID arrive, they wanted trade and manufactured goods. Not gold & silver . Ie.: As if there was a place they could have spent such $$ in the first place. Doh!
There's been extensive archie digs at all the missions. And ... aside from trinkets and some silver reales (fumble fingers stuff), there is NO gold , in any of the museum's dug collections, to my knowledge. Like Carmel mission (where I lead tours), there was extensive digs/sifts from the 1930s to 1950s, during the restorations. And they have dozens of silver reales , lots of cool buttons, crucifixes, etc.... from that. Ok ... where's the "gold" ? Simply not there. And in all of CA, I know of perhaps 8 or 10 escudos dug by md'rs (a few by some friends of mine). Yet hundreds and hundreds of silver reales from the same fellows. And we're talking about some of the most ... uh ... "brazen" guys around who md'd in that era. Ok, where's the gold ?
As for marker clues (symbols , cryptograms, ciphers, etc...) : Me thinks that anyone who runs around studying uncanny shaped rocks, scribbles marks, etc.... : Has watched one-too-many episodes of Raiders of the Lost Ark movie. Not trying to knock anyone here, but ... you asked, so I'm answering.
I've been in on a few cache finds. And been commissioned to find several "tame" ones . Eg.: next of kin survivor relatives call me out d/t they have suspicion that their late grandfather or husband or brother or whatever, had buried stuff. And in each and every case, there's nothing out of the ordinary that would have marked the site. They'd be just at the base of a wall, or the corner of a barn, or under the house next to an upright support, etc..... Nothing conspiratorial, fraternal, mysterious, etc.....
And think of it: If you were going to bury something, it's presumably to "hide" it. Right ? (Lest why else bury it). Ok, then what do they do next ? Riddle the site with clue markers, for someone else who comes along ? Make and pass out treasure maps with mystery symbols for all to see ? It's great for Hollywood and the back of Capt'n Crunch boxes, but , that's about it.
If I were suspecting caches, I'd certainly swing my equipment @ "likely spots", sure. But to try to read into any funny squiggle on a rock, ..... no. But that's just me.