Basically, you get invited to a Coalition which is capped at 5 and when the leader of the coalition joins a town, everyone in the group gets pulled in with him (assuming they are available and ready to go - you need to be at the town select menu and waiting). List your D2N IGN and someone with space will invite you, but we may have to update our groups after this town to see whats what.
As for random towns, that's why we all run in as big as a coalition as possible. It is incredibly easy to grief in this game and one person can screw over an entire town in over a dozen different ways. Someone trying to blatantly injure someone is nothing when you can anonymously poison food/water, kill the entire town by opening the gates or by locking everyone outside, or stealing rare/valuable resources to go jihad in the desert.
As for our current town, we probably have 5ish days or so left if we can't fix our water problem or get the right blueprints. Wouldn't be surprised if it's less due to our randoms throwing the inevitable tantrum.