Tomorrow night is National Night Out. As far as I know, there are about four block parties happening around Sherman Oaks, but I won't list them since they are really for the neighbors on those specific street.
But the one public one is open at the Sherman Oaks Galleria which begins at 7 p.m. Park and go to the front of the mall where the fountains are. If you want free validated parking, LAPD Senior Lead Office, Geroge Aguilar, will have 100 or so passes. But you're going to eat dinner there anyway, right?