Outdoorsclub.org, an organization of outdoor enthusiasts, has organized a graffiti cleanup of Eaton Canyon for Sat., June 27. They will meet at the park parking lot, carpool to the Pinecrest gate, and work on the area between the bridge and the waterfall. Click on the link for more information. You can sign up online, and this does have the official blessing of Eaton Canyon Park staff.
Thanks to Benita Oekawa for the tip.