If you’re new to the area, or new to hiking, a great place to start exploring Mt. Diablo State Park is at the Curry Point Trailhead. It’s the perfect launching point for hikers of all abilities, including those with young children, and its mid mountain location just past Rock City makes it easily accessible.
Located about 1.5 miles from the Danville entrance kiosk, there is a large parking with ample space to launch your day’s activities. The broad fire roads that lead to various trails can easily accommodate jogging strollers if you wish to bring the little ones. Or if the whole family decides to hoof it, rest assured that the hikes are not too grueling. Depending on the time of year, you can see a variety of wildflowers, packs of coyotes, and rattlesnakes (hopefully not packs of rattlesnakes!)
An often suggested moderate hike is one that leads you from Curry Point to Knobcone Point Road. This leads you beautiful views of Mt Diablo State Park and amazing rock formations, including Balancing Rock. This simple trail pretty much dead ends, making for an easy (and not terribly confusing) return loop to Curry Point Trailhead.
For a map of Mt. Diablo and their trails, please visit: http://www.mdia.org/parkmap.htm

Hiking in Danville: Mt. Diablo's Curry Point Trailhead