Most group rides are on public roads (open to all) and most riders don't care about your age as long as you're safe. I was riding with the big guys by the time I was 14 (although I had started racing a year prior). Make sure it's not an exclusive club/group and feel free to introduce yourself at the start. It's best to hang out near the back until you learn how to ride safely and smoothly within a peloton, but chances are you'll be dropped in short order on your first ride (or few rides) anyway.

Russ Roth made a good suggestion to look for a youth program, and local bike shops are likely to be aware of the closest ones. I started out at the local velodrome and was invited to a club by riders there. It looks like this track is close to you, but I don't see any mention of a junior program.
https://nevelodrome.com/event-schedule/

There's also a junior racing subform here, but few people go there.