1100 feet gain
Take the 60 to Moreno Beach Blvd. Exit heading South, follow the curve of the road past the turnoff to Perris Lake. Turn left on Grande Vista, follow it to the end and park. Walk past the water tanks and begin up the hill on a motorcycle track/path.
There is a lot of new construction, so the trailhead may change very soon, but there are many ways to get up into the hills. And you don't have to pay the Perris Lake fees.
I can't say enough good things about this hike. It is short, but steep. You gain great vistas of the major Southern California Mountains and their respective ranges. You are hiking through nearly waterless desert so there isn't poison oak :-).
Even in August, the temperatures cool down enough to hike it just before sunset, or in the cool of the morning, and that is exactly what I do.
I take this hike 3-4 nights a week with my dogs. It is a jaunt pretty much straight up the hillside, and the incredible views of the San Gabriels and Bernardinos begin almost immediately.
From the top you get clear shots of Jacinto, Gorgonio, and Baldy. Watching the sunset from this spot is exhilarating. Plus, I've never seen another soul out in the evening.