As far as police helping out...remember Katrina. MY guard unit was called to go help down there (I was already out by then), and the local police were of no help at all. They were, mostly, more of a hindrance, taking things, than a help. Now, mind you, this was IMMEDIATELY after the fact, and their PD at the time was fairly corrupt. The NG job down there was to recue folks, and prevent looting. I only heard of one person down there that my unit had run into that was set up to survive the disaster. He simply asked to be left alone, he had plenty of stuff, and, well, they did. No orders to distribute his rations, nothing like that. I think that, in a natural disaster of that magnitude, a neighbors call to the PD that someone has more than they do would be flatly ignored.
Law & order, in a large scale disaster, would likely break down. I think that this is largely due to the ay we're wired; most people, when it comes down to it, are out for their own skin; everything else comes second. Perhaps once the shock wears off, neighbors would group together. But, like others have said, I dont see being left alone for 6 long months here in the US. At that point, we either lost the war, were invaded by aliens, or voluntarily removed ourselves from society. Six months of food & water would work alot for bartering, but I would hope you could bget somewhere safer within those 6 months.