I have some ideas for more effectively shutting down Portland, but I also want to call a brainstorming session. We need some dialogue on this!
More affinity groups, spread out across the city. Don't argue with the Police, leave immediately on to the next intersection you choose to block. The idea is to keep the Police running around. Some groups will in the end succeed in stopping things long enough.
large objects that are difficult to move could be used as barriers. just leave them, no people needed. old cars, cement blocks...
take the opportunity to adbust while the cops are out chasing other groups around. but remember, there are cameras everywhere.
Also, I agree with some of the people that have posted their advice to not give the media anything negative. Turning over motorcycles and burning flags, while cathartic, is in the end counter-productive. And wearing aggresive clothing only attracts the attention of the police to you. I'm not saying that one should give up their style for the protest, just be smart!