This is the primary route to the summit of Rattlesnake Peak. This is supposed to be one of the harder class 1 trails in the San Gabriel Mountains, like a miniature of its' larger neighbor, Iron Mountain.
I labelled it "Primary Route", as I don't know of a better name. If you know the actual name, or have a better one, feel free to add it on and I'll fix it ASAP.
Total distance is about 8 miles, according to Google Earth.
From the 60, 10, 210 freeways:
Exit onto AZUSA, head north.
AZUSA becomes R39 (on maps)
Before you reach the Azusa Canyon Off Highway Vehicle Area, you will see a bridge on the right (the only one). Cross the bridge. Continue down that road. On the left side, there is a turn onto Shoemaker Canyon Road. Turn left onto this road. It dead-ends at the parking area.
Leave the parking lot, headed north along the closed dirt road. If you look in the photo provided, you will see that the trail goes off the road after the second large turn. The trail is easy to spot.
This is supposed to be one of the harder hikes in the San Gabriels. Lots of ups and downs. The foliage gets to be a bit thick, with Scrub Oaks and Yuccas.
If you're interested, you can continue to South Mt Hawkins from the summit, taking the ridge to the northwest. One can also access Peak 5021 (Doe Peak) by heading west along the obvious firebreak.
Always bring plenty of water. Stay hydrated, and make sure you bring enough so you aren't dry when you end the hike.
Trekking poles help on the loose soil.
In winter, an ice axe and crampons may be necessary, though rather unlikely, as snow at this altitude is typicall slushy by the time anyone treads on it. Heavy brush keeps it from becoming windpack.
I'm not so sure about National Forest guidelines, but one might want a machete at times, as the growth can be "aggressive". Chances are you won't need it.