Ask your neighbor to try a product called ODOBAN from home depot. I like the eucalyptus scent. You mix it with water for different strengths according to the job at hand. I found it when my husband had a stroke and we needed to start disinfecting more things more often. It has many uses and it smells nice and clean after it is used. I do not know of any plant that can take away dog urine odor. To me it needs to be washed away with a cleaner if it is smelly. I hate to see them rotting out a planter you have with their urine if they lift a leg. I hose often and clean with a bit of the ODOBAN weekly.

I do not sell this product or work at home depot I am just trying to help...

I would skip any rock mulch...soil is friendlier....don't know where you live but I would be planting a dense evergreen like arborvitae or maybe some sort of cypress.....and keep it closely trimmed so it stays dense.......water it often and perhaps overspray a bit to wash their concrete.

And complain to the housing association!

My family has four dogs and our backyard has smelled quite treacherous, at times. We use Simple Green Outdoor Odor Eliminator on the ground and it works pretty well. It has a nice smell that lasts a few days, even after they "go" on it again. I imagine that you could give it to your neighbor to treat their concrete. It might also help if you sprayed it on your side of the lawn to mask the smell. I hope this helps!