film location - Were Poltergist and E.T. filmed in the same neighborhood?

No, they are not the same place.

According to this site, Poltergeist was filmed in Agoura Hills.

Another page on the same site indicates that the street where they take off on the bike (I assume that's the one you're thinking of) is filmed in Granada Hills.

As a semi-related piece of trivia I found on that same site, in the Charlie's Angel's remake starring Drew Barrymore, there's a scene where she rolls into the villain's backyard, and the house is the same one she and Eliot lived in in E.T.