If you go back to the historical street view for that location in 2008 (you may have to move the camera to the other lane, historical street view is quirky), you can see the guerrilla sign. Looks like they replaced it sometime between 2008 and 2011.

Edit: Here's a link:

https://www.google.com/maps/@34.0556515,-118.2563396,3a,75y,...