Interesting subjects here. I just got back from Hilton Head, SC, where they really do enforce the law that cyclists have to be on a bike path if there is one. We were in an area that had tons of paths filled with people who haven't ridden for 20 years on cruisers, joggers, walkers. It was obviously dangerous for my husband and I to be cycling on this path. We got pulled over by the cops twice and just about arrested when i told him we had the right to be on the road; went and checked on the internet and apparently we did not have the right to be on the road. I don't take well to mean redneck cops who are 50 pounds overweight. Later I took my mountain bike on the path to get to a nature preserve; talk about getting pissed off! I was going about 10-12 and had many near collisions. I swear, I never yelled so much, even though i kept saying on your left, bike passing, etc.
I live near mostly country roads, but there's a fair amount of suburban traffic where i usually ride. I have no problem putting my arm out with the stop sign if i think someone is going to do something funky. I also stop if i feel like they won't see the arm. I'm pretty lucky; there are tons of cyclists here in Massachusetts and especially in the area where i live, most people are polite. My worst thing was on a commute home from work, someone was backing out of their driveway and i knew he didn't see me, despite the fact there were 2 others in the yard who did. I yelled really loud and he stopped. I agree with the 2 riding abreast. Some towns around here are starting to give tickets to large cycling groups who do this. It's dangerous and I see their point.