To get down to Serrano Canyon from the Conejo Valley side, you must meander your way down the steep Sycamore Canyon Fire Road seen above. Have fun and don't think about the challenge of making your way back up this hill later in the day, when the sun is beating down on you!
Continue on down Sycamore Canyon Road, pass through the Danielson Multi-Use area, the National Park Service house and the old barn-like structure seen above. You can actually get to Serrano via the Blue Canyon Trail entrance point just east of the Danielson Multi-Use area.
A little farther down is the Serrano Canyon Trail trailhead. Two or three miles into this trail and you'll be in Serrano Canyon. Warning...this trail has had some fairly well overgrown sections in my times in there, so definitely be aware and consider long pants. I ran through there and survived in shorts but the poison oak on the sides of the trail were nervewracking enough to make me consider turning back.
There are several pieces of old farm equipment in the canyon. Makes you wonder about the history...There are several ways out of Serrano Canyon but my choice was to follow a trail that loops back around to Sycamore Canyon again, about a mile or so north of the entry point and south of the Danielson Multi-Use area.