Bobcats definitely exist in your area. They are very rare in sightings and will usually know of your existence long before you will ever see one. They usually do not pose a threat to humans as they are very secretive and will almost always avoid contact with humans.
Mountain lions, also known as cougars, also exist in your area, but are rarely seen. They range from 100 to 200 pounds and are from four to five feet in length. Although attacks upon humans by mountain lions are very rare, they have occurred in Southern California.
Avoiding Being Attacked
The general advice to avoid being attacked by a mountain lion is to travel in groups when hiking.
If you encounter one by yourself or with children, stop and make yourself look as big as possible. Pick up small children and put them on your shoulders to make you appear even larger.
Aggressively defend your position. The idea is to deter their attack by making them think that it isn't going to be easy for them.
Pick up a rock or branch to help fight them if needed.
Don't run away as this makes them think you are prey and may encourage an attack.