Find a way to get him to stay and connect the wires.
Detailed walkthrough
If you opt to convince Dean to stay by making it safer for him, you will have to activate two holograms. The terminal to activate the first hologram can be found nearby, through the door opposite the one you just came out and down one level/floor. The second hologram is across from the first a little further away from Dean, on the second floor through a hole in the wall. Access to this terminal is through the ruined cafe which is further away (look for the door on your Pip-Boy map). Inside the ruined cafe, take the stairs up and go through the eastern door to Puesta del Sol south. From the balcony, walk to the left where there is a break in the balcony walk through in to the hole in the wall, and the terminal is directly in front of you.
(Optional) Turn on both security holograms to guard the courtyard below Dean.
3
Let Dean know it's safe for him to get to his gala position.
Notes
On the second floor inside the ruined store, (follow the balcony around across from the second security terminal), is a queen sized bed with a blue cover that can be slept in, regenerating health. If you sleep there when you are playing in Hardcore mode it will activate the sleep requirement count.
If you have not gained the Sierra madre martini perk yet, it is best to do it before you complete this quest otherwise you will not be able to get it without the use of console commands.