On Sunday, I didn't know scottawr had just gone up to the mesa from the bottom of the Trabuco Canyon trail. It was one of three stops I made on a balloon style loop coming down from the top of Trabuco Canyon. I hit Vicker BM above the Los Pinos saddle, then down Trabuco Canyon to the Yaeger Mesa, returning up the West Horsethief trail, then over the top of (unoffical) Horsethief Peak. 14 miles round trip and about 3875' of gain. Starting on Main Divide Road near the Blue Jay and Falcon campgrounds, I went up 1.5 miles to the Los Pinos saddle, then a firebreak to Vicker which rises about 100' above the road.
Heading down Vicker to Los Pinos saddle
Los Pinos saddle is the junction of Main Divide, Los Pinos trail, and the Trabuco Canyon trail. This was my first time on the Trabuco Canyon trail and it was lush near the top despite the dry winter. I passed the junction with West Horsethief trail to continue down to 2400' to look for a trail up to the mesa. There were several side trails descending to the bottom of the canyon, and I ended up passing the one that crosses the canyon and heads up to Yaeger Mesa. Instead, I descended all the way to 2246' where I spotted a duck and followed it into the canyon, looking for some way up. I went in circles looking for a trail, and ended up wasting about 30 minutes and some energy thrashing around the brush and boulders.
Upper Trabuco Canyon trail
Still Xmas in Trabuco Canyon
Trabuco / West Horsethief trail junction
Lost and boulder hopping looking for the Yaeger Mesa trail
Eventually, I headed back up and took the most likely looking trail along the canyon wall, and it turned out to be right. After a short lunch break, I headed down and spotted the wreck of a PT-19 (WWII era two-seat trainer) just below the mesa on the right (heading down).
Yaeger Mesa trail on the south side of the canyon at about 2400'
Yaeger Mesa, see scottawr's report for better photos
Plane wreck just below the mesa
Back in the canyon, I started the 1600' climb out along West Horsethief trail back to Main Divide Road. The switchbacks are long and there is not much new to see along this stretch except great views of the mesa. When I got back to the road, I took a right and got my first clear view of Horsethief Peak. The road gave up some elevation before I reached it. The first firebreak I came to went up from the north. It starts with a 15' dirt wall and the last couple of hundred feet is completely overgrown in spots with manzanita and other brush. I came prepared with my machete and hacked a path through the worst of it. Even though I cleared some of it, I still recommend avoiding the north firebreak and going up the south firebreak which is clear of obstructions.
Yaeger Mesa from West Horsethief trail
Shoe near the top of the West Horsethief trail/Main Divide junction
Horsethief Peak
Deep wash on the north firebreak
Vicker (left) and Los Pinos (right) from Horsethief Peak