After I moved up here to Marin, Ca. from the East Bay (El Cerrito) I found that roadies in Marin mostly do not wave. Now, roadies in Marin many times are not from Marin, so I always take that into account.
I'm a goofball, so I wave a lot, sing to myself, talk to the birds and squirrels and whatnot. I also try to flash a peace sign for cars who recognize my presence in traffic.
Why not be friendly, right?
Now when someone pulls some aggro BS, be they cyclist or motorist or even (very rarely) a pedestrian, I have some choice combination curse words at the ready.