Probably the most famous alleged haunting in Southern San Diego County took place on Otay Mountain, where border patrol agents reported seeing the ghost of Luis Santiago, an agent who fell to his death on patrol. After a smuggler died at the same spot where Santiago had fallen, Santiago's ghost was never seen again. Agents on patrol there believe that his spirit was at rest, having taken revenge on the man who murdered him. 
These incidents were recorded by Rocky Elmore, a retired border patrol agent, in his book, Out on Foot: Nightly Patrols and Ghostly Tales of a U.S. Border Patrol Agent.