There's something very simple that everyone can do to make the city better. Report any grafitti you find to the city, and they will quickly come out and clean it up. You can even do it online...
http://www.fresno.gov/Government/DepartmentDirectory/Police/Neighborhood...
There is no excuse to tolerate grafitti and nothing drives property values down like some unwanted spray paint on a fence.
What gets me is how some people ignore it and allow grafitti to remain. Don't you have any pride in your neighborhood? Get off you ass, and if you're not going to paint it yourself, at least call the city. You pay for it anyway.