Key words here are Cached in the Seams of the rocks which is referring to an area where there are multiple levels of rocky terrain that have dips or holes in the terrain that would be ideal to hide something. The treasure also has to be buried in an area that isn’t exactly accessible to humans but not impossible to get to because the people who buried it had intentions of getting back to it right? So where in San Marcos is there a rocky terrain with dips or holes in the ground that would be ideal to hide something not to mention it is difficult to navigate but not impossible to get to? That sounds like It could be along a river or hiking trail. Boom. Feel free to use this information in your own way.
