Don't let the fact that this trail goes down a canyon fool you into thinking you can coast down.. You can't. Quite a bit of pedaling is required on this trail.
The pipeline trail has a fairly long season - from about early April till late October / early November (gate near Porter Fork is closed from late October to July 1st. As long as snow is clear, you can access the trail by riding up road from gate).
This trail is popular as a shuttle route - park at the park and ride off 39th South near the mouth of Millcreek and drive to Elbow Fork (the beginning of the trail). Many also do it as a loop by riding up the road and returned via the Pipeline.
There is also alternate access to the trail near Porter Fork and Church Fork - however Church Fork is quite the grind.
If you really want a challenge, you can ride UP the pipeline. Be warned though, the end of the trail (or beginning in this case) is Rattlesnake gulch - a very steep. loose and rocky climb. Most will have to hike-a-bike portions.