It's a bit of a drive from SLO, but the trails out at Montana de Oro are top notch. My mom lives near there and when I visit her I run the trails at MdO. You have a choice of steep hills and flat bluff trails. A few days each week PG&E opens the gate at the south end of the park so you can go on the coastal trail toward Diablo (Pt Buchon). I was able to run out there one time I was there. Beautiful.