Good news! The Legacy running/biking trail is connected to the Jordan River Parkway trail. No more hitting dirt or construction signs. Thirty miles of not having to worry about getting hit by a car is well worth driving to.
If you're starting on the Legacy side be sure to go to the bathroom before biking as there are very few places to have a pit stop (although it does make you go faster). If you're on the Salt Lake side, you will have to cross the occasional road but there will be crossing lights.
Do watch out for the occasional moron with a dog on a leash who feels the need to take up both lanes. And when you call out "on your right" they jump — not off the trail — but across the trail dragging their dog and leash in front of you. Next time I'm not crashing my bike to avoid your dog since that leaves road rash — I'm just taking you out.