It took me a few years to get up the nerve to go riding with a bike club, but when I finally did, it was no big deal. There were people faster than I was and there were people slower than I was. Everyone was nice. I did have to get a cycling computer for my bike so I could use the cue sheets ("turn right at mile 21.3"). I don't know why I hesitated so long. Like you, I had ridden by myself for years.