In this area, making a decision based on the use of a vehicle's turn signal will get you in deep trouble quickly. As a comedian said, if you see a vehicle with the left turn signal on you can rest assured he bought it that way. I am sure I did not quote that correctly, but you get the basis of the quote. Anyway, I mostly try to allow the traffic to clear if there is not a well marked turn lane, but then again you can get in trouble with marked lane use also. Just watch the movement of the cars very closely and do not assume anything.