I've got to disagree with the replies you've received. I'm an RN, current charge nurse on a locked, in-patient psychiatric unit in a large city. However, I used to work as an ER nurse for ten years.
It is illegal to treat minors without parental consent EXCEPT in a genuine emergency. Life-threatening illness will take precedence (as it should) over parental consent.
However, minors with lacerations needing sutures, or minimal assessment just waited in the ER until the parents could come. An exception was if an adult was with the minor who had a notarized consent from the parent to sign for treatment. That happened occasionally when gr/parents had the kids during a trip by the parents.
As for letting your 17 y/o d/d out into the night without a ride, we would never do that! If no other option was available, we all chipped in for cab fare to get ANY person (not just a minor) home safely. We didn't think it was a big deal either. We just couldn't in good conscience put anyone out on the street alone at night...