Jasmine, clematis and honeysuckle will take up an awful lot of space,, both in height and spread, but if your wall is not high enough to block the view, then unless you've installed trellis or something on top, the climbers won't get high enough to do the job, they all need something to twine or climb up. If all those climbers are planted in a small area (less than 12 feet minimum in width), planting anything else is not really an option, but for instant view blocking, buy an already tall clump of bamboo, put it in a large pot, and stand the pot in the appropriate spot. You can move it later as the climbers start to take over the world....

Note that I'm not suggesting planting the bamboo in the ground - most will run and spread widely, unless you choose a Fargesia variety.

Some statistics would be good:
How big is his window and how far away from your window is it?
How tall is the wall now? By "the wall faces south" does that imply that your window faces north?

How big is the area you want to screen and how tall does the screen need to be ?

Of course none of this matters if Bamboo's suggestion will fill the bill.

welcome to GoY.

I agree with both the posts. does the owner of the man cave intend to spend a lot of time in there? are you on good terms with him? if you are could you ask him if he plans to screen his man cave from you?