Hm, couple of ideas inspired by your pictures. Would anyone object if you fastened some cedar lattice on the wall? You could attach it to that blue railing on top of the wall and give your ivy some more place to climb. That would be by far the fastest, cheapest screen solution.
When you do renovate, how do you mean that area 'won't exist'? Will you be allowed to move the wall out to right beside the path then? Surely the building codes won't allow you to build an addition out to the path? So will you have an enclosed garden inside the wall, or a patio? You'll still need tall screening plants, I would think.
Reason I'm asking this is because you could 'invest' in some small trees with the intent to grow them in large pots along the path, then move them when your remodeling happens. Something like short palms or even clumping bamboo? If you're worried about the pots 'disappearing' you could chain or cable them to the posts of the little wood fence there. But if the pots are large enough, they'd be too heavy to move easily anyway.
A really fast-growing plant for a quick screen would be Mexican Sunflower, Tithonia diversifolia. If I needed a quick screen this would be my first choice. It grows easily from cuttings, and will get up there to 6 or 8ft. very quickly. If you keep it watered, you will need to cut it to keep it at the height you want, but "cut" is a relative term, because you can just break off the tops of the tall growth by hand. Easy, quick, cheap, and it blooms spring and fall here, so it's really pretty as well. Find someone with a plant and ask for cuttings. Root them in water and you're off!
Mexican Sunflower (Tithonia diversifolia)
