One of my co-workers began bike commuting this week. After the initial thrill wore off (for me), I asked her if she had any problems or questions. I am familiar with her route and there are a couple of tricky spots on it. She actually did have some questions about safely getting under the highway, so I told her the best way to do it and I added as an afterthought, "Be sure to ride with traffic." I don't even know why I said it, but she was like, "I'm so glad you said that! I couldn't remember if I should or not."

The point is, sometimes if you haven't been on a bike for awhile--or riding on streets ever--it can be nerve-wracking and you might not remember all the rules or think clearly at first. So if you get a chance, yeah, I'd say something to help them, and you, out.