Riding in a group is scary especially when you don't know their "background". Most clubs that cater to many levels of riders (i.e. have A,B, C, rides) offer a class or a series of training rides that focus on bike handling skills. Some of the more "serious" clubs assume the riders know how to stay in line, draft, point/call out obstacles, etc. (they don't necessarily!). The best thing I ever did was take those training rides with the NYC Cycle Club - you had to learn how to ride in NYC traffic and on winding roads with suburban drivers, and bike handling, and safe riding skills were taught. If your local club doesn't offer a class or training rides I'd seek out one of the bigger organizations that offer weekends for beginners/intermediates that teach the basics of safe riding - they are good even for non newbies. Riding with people who are knowledgeable and safety conscious is SO much better!