While I've never understood how large puppet parades and haphazard street performances help further the progressive causes of reducing poverty, restoring civil liberties, and stopping corporations from influencing government, people should have the right to engage in whatever lawful political expression they see fit. That means not having to experience being shot with a taser for pissing of a cop (Nothing pisses off a cop like people exercising their rights to assemble and express opinion.).
You can keep up to date with the latest G20 happenings via the BBC's Live map. It's an interactive resource with text, image, and video updates linked to a map of London. There are also live blogs going at The Guardian and The Huffington Post.