All of the sarcasm when there is really something to be seen!
To me, it appears that the bird (not sure it is a Dove) is looking at where the treasure is buried but the skull is saying there is a death trap and may be telling you to find another path to the treasure.
I am guessing a tomb or maybe several tombs in the area nearby. The doves may be representing peace in the afterlife for the dead. There may be at least some cool relics to be found in the area from previous inhabitants.
I believe you are somewhat right! It looks like they used some natural features for the large skull but the eye on the left (the skull's right eye) appears to have been chiseled or excavated out but then suffered a rockslide in recent years. I can't tell much about the one on the right. Reading monuments, signs and symbols left by the Spanish and others, is just not my thing but I happened to see the features when I blew up the picture!