My advice would be to smile and wave.
Eventually it will go viral and everybody in LA will be smiling and waving to each other.
If you are regularly grouchy while you are riding with hundreds of cars, then talk to your doctor and tell him of your situation. Tell him of the social anxiety.. tell him of the stress and pain experienced on your communte and that you want to get to the point where you are so happy all you can do is ride, smile and wave.