Vinyl is a solid surface and most graffiti can be removed with some products including:
These products will take the graffiti off with a little scrubbing and will not damage the vinyl. Before graffiti happens, spray a coat of Armor All™ on the surface of the fence to make it easier to remove graffiti.
Wood is a very absorbent surface. There is really no way to take graffiti off a wood fence without altering the wood.
A pressure washer will take graffiti off and take the wood back to its original state, requiring refinishing. Another method to try is to use a steel wire brush with mineral spirits or just repaint the fence.
Most power poles are galvanized steel or wood. Galvanized steel poles can be cleaned with almost any chemical and will not hurt the pole, even acetone, and mineral spirits. On a wood pole, use a pressure washer or repaint the pole.
Mailboxes are usually solid surfaces and can be cleaned with Krud Kutter™, Tag Away™ or Graffiti Scrubs™ with a little scrubbing.
Cinderblock or brick walls are very porous surfaces and take a little more work than most surfaces to remove graffiti. A few options to clean these surfaces include:
Spray the wall with an anti-graffiti chemical to make it easier to clean if vandalism occurs.
Most of the products mentioned above can be purchased at: