I've ridden that closed section a few times with my brother. I would not ride it solo due to the hazards and desolation. With that said, the ride and views are awe inspiring. Sad to say, if it is ever opened, it would just be another race course for wannabes and that would ruin it for cyclists unless one rides weekday mornings.
It could make a more user friendly experience for an alpine tour of the San Gabriel Mountains before crossing over to the San Bernardino Mountains.