Old Juan Carlos was a legendary bad dude around these parts. He is said to have accrued much treasure through nefarious means, and hired peons to hide it near his cabin on the shore of Lake San Luis. Well here's a picture of what you're up against. It's in a State Park Wildlife Refuge too. Lotta ground to cover, and no cover to hide from the rangers. Good luck.
If you love treasure hunting and codes, check out my Armchair Treasure Hunt Game!