Hiked an out and back with my wife from Hidden Valley Regional Park. About 5.0 miles round trip with about 1500 feet of gain. The bottom section is very steep, exceeding 30% in several sections. The middle section wraps around the mountain in a northeasterly direction, and is a pleasant single track. The trail disappears in the last section heading in a southerly direction over the ridge line to the summit, which is marked by a cairn. Descended via the same route. About 3 hours round trip (2 hours up, 1 hour down). We saw lots of horse dung, but unfortunately no wild horses at all. Great views of Reno!
Went from the paved parking lot listed as trail head #3. My mileage came to about 1.4 miles each way, I think this is mostly due to going straight up the hill as opposed to following the use trails around the side of the mountain. Either way it was a 1400'+ gain so it wasn't necessarily the most gentle path. Took an hour up and about 45 minutes back down. Grabbed a pair of Geocaches while I was up there too.
Was with the Sierra Club on this one, so have no idea how we actually got to the trailhead (the page description seems a little different). Incredibly steep in some places (and a little hard to navigate on the descent). RT was 3 hrs for us; great workout.