Nice trail without leaving the city. Light-moderate but not difficult. Short enough to do in the morning or afternoon and still have a whole day to do whatever else. It's a loop. Go clockwise for a more strenuous hike, counter-clockwise for an easier hike. Starting to the left first will give you more uphill battle. Going right first is a lot more gradual going up. Views of the LA horizon are amazing. Morning or evening is best for pictures and viewing. Mid-day from late-morning to early afternoon is a view of smog covering the city and it's too hot. Lots of dogs on this trail, and you're allowed to unleash for part of the trail.
The trail was decent. Moderate too difficult climbs depending where you start. There were pretty good views of Hollywood. The bads are there are little to no bathrooms and parking is horrendous. I recommend Hellman in Whittier it's comparable with out the crowds.
Fredrick O. on Runyon Canyon Trail
Not a tough hike but great views of the city. Dogs can go off leash as long as they are well behaved. Can get pretty busy on the weekends.