My experience is that what most groups say they "average" is what you look down at your computer and see most of the time, but more than what you have on your computer when you finish. For example you may look down and see 18-19 most of the time but if there are very many hills your average will be 15-16. I don't like no drop policies personally, I think they are an antiquated tradition from before there were cell phones. No one carrying a cell phone and proper flat fixing gear is going to be "lost". However, I do believe if your ride has that policy they should stick to it, and asking people to not show up is not how to do it. If I were you I would find a different ride.