Lance Creek is located south and downhill of the nice singletrack route that completes the outer Bull Mountain loop. When riding the main Bull Mountain loop counterclockwise (the direction I recommend), shortly after crossing the big creek at the bottom of the rough doubletrack descent after the cabins, hang a left past the gate. The gravel road/doubletrack then forks, and the main loop heads uphill. Lance creek heads straight.
The "trail" is basically a boring gravel road/doubletrack up until the last half mile or so where it turns into a horrendously washed out climb that is almost completely unnavigable by bicycles. The trail is covered in large, loose babyheads.
Long story short: this was a miserable trail that didn't deserve to be ridden. Even coming downhill from the other direction it wouldn't be much fun. Skip it and ride the main outer loop.
The steep climb at the end of the trail saw some significant maintenance a couple of years ago, and while still heinously steep, if you have lungs and legs of steel it IS actually rideable. It is undoubtedly still a challenge, but this trail does serve as a good way to do a medium-length version of the Bull Mountain loop.