There's all kinds of group rides in larger urban areas, from race pace to very casual. Perhaps not as much in more rural areas.
I notice that the local cycle club rides can be faster than the advertised pace later in the summer. These rides often have a core group of regulars that get faster during the riding seasons. So if everyone seems to be doing okay, they may pick up the pace. It's probably good to find a ride that sounds a bit too easy, just to get started. Being new to groups and having to do an all-out effort isn't as safe.
But yeah, a couple of mph faster than your usual average is often typical. It's the draft, but also the motivation to not slack off briefly!