sundaypunch, you are correct that those are the proper signals.
However, until drivers' education is mandated in this country (USA), I'll point in the direction I'm going to turn, as I feel it is less ambiguous that the "legal" method of signaling. I would believe that most drivers around my neck of the woods have no idea what the legal hand signals are (or they have forgotten them).
I generally try to follow the traffic regulations. However, sometimes my instinct for self-preservation overrides the regulations. I generally ride in the street, in traffic, but on rare occasions, I'll take the sidewalk (which I hate doing, but sometimes it is the more prudent option). I will take my lumps if a cop decides to enforce the rules. Thus far, no problems (crossing fingers).
I don't always signal right turns, as it isn't always necessary. Left turns are usually signaled.