The great thing about bicycles is that while riding them, laws no longer apply to you! Whee!
Don't make any assumptions about the skill level of other riders that you see. The number of people on bikes has skyrocketed in the last year or so (at least in Northern California). "Nice bike and helmet" could just mean that the person bought what was recommended to them by an LBS employee.
Also, for some reason, it's "common knowledge" that one should ride facing traffic. Blech.