Down Euclid, roughly halfway between Malvern and Bastanchury, is a sign for Hiltscher Trail. There's a very small dirt lot that holds about 8 - 10 vehicles.
While the park starts at Euclid, Hiltscher Trail starts across Euclid over on Valley View. It ends at the Juanita Cook Trail, right next to a water fountain with a well-placed dog bowl for thirsty pups. The entire Hiltscher Trail is 1.39 miles of well kept, relatively smooth dirt path and is great for running, walking, biking, strollers, or horseback. The tree canopy makes it a solid choice for a summer run. I saw a family doing a professional photo shoot, too.
There is a little stream that runs through, so gnats might gather on the trail.
Hiltscher Park offers faux-seclusion because it is more woodsy and overgrown than a traditional park. The hum of lawnmowers and sun bathing older gentlemen will remind you that you're still in Fullerton.