I was born and live in Sao Paulo, and this law (Lei Cidade Limpa) really helped to reduce the visual pollution here.

Here are some links for pictures of before/after. For more images, you can search for images of Lei Cidade Limpa SP or Lei Cidade Limpa São Paulo (we use the tilde here, you can remove it if you prefer)

http://www.flickr.com/photos/tonydemarco/sets/72157600075508...

http://www.flickr.com/photos/sueluzfotos/page4/

http://ftorquato.wordpress.com/2008/08/26/gilberto-kassab-de...

And here's a link with a article in Sao Paulo prefecture about this law (google-translated to English).

http://translate.google.com/translate?hl=en&sl=pt&tl...

Cheers, -B