The Quail Hollow Trailhead sits at the mouth of Little Cottonwood Canyon, and its trail takes you alongside the creek on the way down to a large open park with a few intersecting trails and off-shoots. This isn't an ideal mountain biking trail because of several large rocks along the tight singletrack and because its often filled with hikers. What it does offer is an easy-to-access option that doesn't require you to head up the canyon and a fun trail that starts off with the descent. After riding along the creek in a small valley you'll drop down to Quail Hollow Park. Circle it counter-clockwise and head south and then west along the long doubletrack dirt road toward the water towers. There are many places to get some speed on the descents, but the overall ride doesn't last very long without doing an extra loop around the park and heading to the water towers, which gives you about a 5-mile ride.
You can extend the length of the ride by circling the park a few more times. You will see several small trails branching off in various directions toward the nearby neighborhoods of Sandy and Granite as well as along the upper trail. It is better to ride this trail in off hours or you will have to yield to a lot of hikers. While there may be more dynamic and scenic rides in the area, Quail Hollow isn't bad if you are short on time or don't feel like driving too far.