There is only limited street parking on San Francisco Ave at the start of Quarry Road Park trail. If the gate at the intersection of Quarry Road and South Hill Street is open, you can park along the very wide section of Quarry Road. Stay to the side, because a few big trucks drive the road to and from the quarry. Although dogs on leash are legal on the trails above Quarry Road, I think those trails are too narrow to be reasonable places to walk dogs.
The trail starts from the intersection of Inyo Street and San Francisco Ave, where there picnic benches and a community garden. The run is divided into two distinct halves.
The first half is actually on Inyo Street. There are barriers to prevent any vehicular access. The road is wide, paved, and has a gentle uphill slope. Both sides have trees and bushes. One side is an uphill slope where the space between the trees and bushes is covered with vines and flowers. This part has a lot of invasive plants such as French/Scotch broom, Italian Thistle, and Himalayan blackberry (distinguished from California blackberry by its thicker stalks and much bigger thorns).
The second half starts where Inyo Street intersects with Quarry Road. Quarry Road is not closed off, but it is very wide and the traffic consists of an occasional truck going to and from the quarry and occasional cars for people who park along the road and hike from there. The uphill side runs entirely along the boarder of the San Bruno Mountain Ecological Reserve, which is maintained by the California Department of Fish and Game. Most of the plants on this side of the road are native, although there are a few invasive species. The park ends at the gate to the quarry.
Once you get away from the road, the Ecological Reserve is one of the finest areas of native chaparral and grasslands in California. It has hundreds of native plants and many butterflies. A number of species are rare or endangered.
Starting approximately at the intersection of Inyo and Quarry roads, Fire Road 3A
climbs to the top of San Bruno Mountain. About 20 yards farther on Quarry Road, there is a path that loops through the Buckeye Canyon section of the Reserve. About a quarter mile farther up Quarry Road, another path climbs up a ridge to the top of the mountain. The trail that wanders through the Owl Canyon section of the Reserve branches off to the right about 100 yards up that ridge.