Both pretty good ideas (bands and sign). I agree the beginners will not wanted to be labeled as such, but if the instructor "recommended" they wear the bracelet it might help.

"If you wear this green band the guys will know you are just starting and will help you out if you get into trouble. Anyone wearing a red band will help you if you need it at any time ... that means they are volunteering to help beginners on that day."

That would have made me wear a green one when I started. I remember being terrified I'd get in someone's way, or do something wrong and piss someone off, or hurt myself.

If I'd known who was friendly and willing to help me out it would have been a lot easier than going to big beach to ride alone.

Put me down for a mentor, helper, volunteer or whatever you want to call it, and I will wear it every time I ride ... as long as it doesn't secretly mean I am gay or something.