I've created routes many times with ridewithgp and exported as a TCX file to the Garmin 500 and the turn-by-turn directions works fine. From what I recall, I did have some problems when taking someone else's route and editing/resaving it. It always worked better creating your own from scratch. It has been a while since I've created a map though, so not sure if there's been changes to their program. I used the free version.

When doing it this way you'll get one screen that shows turn-by-turn directions and another screen showing the breadcrumb trail. You can choose whichever screen works best, or toggle back and forth.