I think the choice a reasonable person makes is based to a large degree on the belief that SAR will actually happen in a somewhat timely manner. If you believe that a reliable friend at home has your back ( which is what happened in this case ) and will send out the cavalry to look for you then the best course of action is just chill the fk out and wait. Make the best of the situation. The end of Gold Valley road ( google earth) has a stand of trees, a promising sign that you may find a water source in the desert. Clearly having a reliable EPIRB system and / or satellite phone is the best option as you can start rescue immediately by your own actions. If you had not told anyone or had no emergency beacon device then based on the remoteness of Gold Valley road you would best try to get a self rescue going sooner than later. Given that they had driven in and with just basic directional knowledge, enough water, some food and traveling when it's cooler then self rescue would be very do-able imho. The third option of hiking down to Mormon point is not completely un do-able but would require a higher degree of survival skills. Having knowledge of the area is key, if you grew up in that area and knew every inch of the terrain then clearly you would have a major advantage over someone who is learning the area for the first time. Initially hiking up to the ridge line either North or South of the canyon would make the hike down a whole lot easier and safer than attempting the canyon route. Based on what I've read really the only way to successfully hike the canyon is having equipment and repelling skills to overcome certain sections.