While I was living in San Luis Obispo I would frequently climb Mt Madonna. The trail head was less than two miles from my place which made it an ideal natural free gym for an early morning hike. The entire trip to the top and back is 3.9 miles, and there is a thousand foot elevation change. From the top you will find some amazing views. I used to have a meetup group and this was one of my regular hikes. Few people will join you for a 5am hike.