If you're in the clear and have visual contact with obstacles, then go as low as you need to go. Otherwise, stop at the minimum IFR altitude, if it's above your target altitude. My target is to get down to 14,000 ASAP, and then lower when able. There is no rush to get down below ten grand, and if terrain or obstacles preclude doing this safely, don't. Once you get down to breathable levels again, you have time to sort out what you'll do next.