Originally Posted by noisebeam

More thoughts...
Your commute average speed and the average speed the group says they ride really have nothing in common, nor are they a measure of if you can keep up.
Your commute average speed probably includes many more stops, slowing, no drafting.
The club reported average speed is probably what they most often see when they check their speed during a typical paceline.
What will determine if you can keep up is if you can sustain (while drafting) their cruising speed and how fast (and long) you can go for bursts of speed. (sprints, downhills)
Al