Ads themselves are EVERYWHERE. Frequently billboards are placed atop or on the side of crumbling apartment blocks, making it look preferable to live in the billboard itself. This is not so different from New York, now that I think of it.
We drove past a small roadside park today -- essentially a glorified median strip for the beautification of the highway, with the name of a prominent politician on a sign as the man who kept it looking beautiful. It had flowers, small plants, lush grass... and poles in the grass, with ads on them. No oasis is unspoiled in a city of 16 million.