Rancho San Antonio County Park offers good hiking and trail running. Several challenging trails through this park lead to Black Mountain, whose summit is located in adjacent Monte Bello Open Space Preserve.
Weekend parking is a little hard but be patient. I routinely do the four miler (look for signs). Nice respite from everyday life. PGE is mostly an uncovered trail but when you are back on coyote trail, you'll be shaded with trees. The trails are a tad muddy but the streams are filled with water for that peaceful and serene sound. Have fun!