This has been a pet peeve of mine for, well ever, since I learned to drive certainly. Please, please, please, please use your turn signals! I was almost hit a week ago when a car was on Washington heading west (or so I thought since he had no turn signal) and I was on Washington crossing Prospect heading east. It was dark, but I had a front light on and reflective clothing. The car ended up turning left (south) onto Prospect and came within inches of my bike. I had the right of way since we were both at stop signs and I arrived first and was going straight. I was in the street. I had a wary eye out for the driver because I know often drivers do not use their signals when no cars are in front or behind them. Use your signal EVERY time. I don't care if the place is deserted, use it.
Yes, cyclists need to signal as well. I try to, even when I don't see anyone else around. The only times I don't signal is when I can't spare a hand from my bike to keep it upright. This is an issue with a full load on my bike and making a turn. I wonder if we should have handlebar lights that can be used as signals. I wonder if cars would notice them. Sometimes I think we are completely invisible and it doesn't matter what we do, drivers will never see us or care. I mean they never seem to have any negative consequences to hitting a pedestrian or driver. Oh to live in a place where pedestrians and cyclists were respected instead of loathed.