Quick two stage multi at the southern end of the Oso Creek Trail. The above coordinates will take you to a 4 panel sign. On the panel that is facing Marguerite Parkway, find where you are located ("You are Here"). There is a red circle with a number on it. Find what that number is representing using the map key. Enter that name (without any spaces) into certitude and the final coordinates for the cache will be given.
The final is a short walk/drive away. BYOP and use stealth if needed.
You can validate your puzzle solution with certitude.