Late-summer hiking in East County's Cuyamaca Mountains is rewarding, as long as you avoid the heat of midday and early afternoon. Lately, intense afternoon thunderstorms have dropped considerable moisture here as well as farther east, but these are likely to diminish as we move into September. The following seven-mile hike, which stays between 4000 feet and 5000 feet of elevation in the Cuyamacas, is perfect for the last three or four hours of the day, when afternoon shadows lengthen and deer and coyotes make their appearance in the grassy meadows and amid the oaks and pines.
To reach the starting point, drive 4.8 miles north on Highway 79 from its intersection with Olde Highway 80 near Descanso. At this point (about 1/2 mile beyond Green Valley Campground), drive into the large turnout on the right, next to a bridge over the Sweetwater River.
On foot, walk north over the highway bridge and immediately turn left to reach the West Side Trail. Go north about 0.4 mile, paralleling the highway, then bear left on Japacha Fire Road. You now wind uphill, following Japacha Creek, and after about 0.8 mile cross the creek. Bracken fern, sword fern, thimbleberry, and wild strawberry thrive in the shade of oaks and sycamores along the creek bottom.
When you reach the West Mesa Trail, turn left and climb southwest through a magnificent conifer and oak forest. Cross Japacha Creek once again. To your right, 0.2 mile past the creek crossing, watch for the small footpath leading to Airplane Monument. There lies the weathered block of a 12-cylinder engine and plaque reading "In Memory of Col. F.C. Marshall and 1st Lt. C.L. Webber who fell at this spot Dec. 7, 1922."
Returning to the West Mesa Trail, you continue around a hairpin turn and start to follow a ridgeline. (The Monument Trail branches south from the hairpin turn, providing a shortcut to Green Valley Campground if you want to bail out of this trip early.) Continue for 1 mile on the top of the ridge, staying left at the next junction. Just afterward turn left on a narrow and quickly descending path, the California Riding and Hiking Trail. Turn left off of that trail when you reach Arroyo Seco Road, and continue downhill into the Arroyo Seco trail camp.
The camp lies at the south end of a wide meadow frequented by mule deer and other wildlife. To loop back to your starting point, continue downhill on Arroyo Seco Road toward Green Valley Campground, 1.5 miles away. Before you reach the campground take the cutoff trail on the left that slants over to West Side Trail. Then follow West Side Trail over to the Sweetwater bridge.