Whiting Ranch is located in Foothill Ranch and is full of trails for hikers and bikers. There is a wide variety of trails to be found here. Some sections of the park including Vista Outlook and Dreaded Hill are great for inclines with great rewards at the top. The top of Vista Outlook has a picnic table to sit and enjoy lunch overlooking the hills while Dreaded Hill has a memorial bench for a biker that was killed by a mountain lion in the park 10 years ago. There are two entrances to the park. I like to start in Foothill by Ralphs. Make sure you grab a park map before heading in.
My favorite trail route is: Borego to Mustard to Billy Goat to Cactus Hill to Santiago to Sleepy Hollow to Whiting Road to Four Corners back down Mustard and out through Borego. This is about 9 miles and will take a little over 3 hours at a steady pace with a few water stops.
Check it out here: http://ocparks.com/parks/whiting/