I'll usually pass or wait, depending on the circumstances. If traffic is light on the left, then I'll go for it but hug the side of the bus. If traffic is continuous, then I'll wait. Sometimes I'll even pass on the right, on the side-walk which here in Korea is a sidewalk/bike path--really terrible idea, but I have the option. Guess it wouldn't be the end of the world if you did the same thing in the states and just used the sidewalk to pass. Also, since you're leap-frogging the bus, he knows you're around somewhere and is probably aware by the 2nd or 3rd time he sees you that you're gonna continue popping up. Sometimes a bus will insist and going first. Sometimes they'll let me go. But I never assume that I can pass him on the left.