Originally Posted by
Barrettscv
I'm also concerned with safety, ..
I ride with a couple of groups weekly. There are drawbacks, and safety issues from within you own group is one. Another is the group will often hold you back if you are a strong rider, over time you will adopt the habits and general performance profile of your group.
I think they are fine social opportunities and a chance to explore routes you might not ride solo. It's also a reason to dress up in your kit.
Trainers are more likely to be serious business if you are managing bike fitness.