I was in a similar situation as you, I was a recreational rider on a hybrid and was hoping to get more into the sport. However, I found myself WAAY out of my league when I started joining clubs. I haven't encountered any clubs with people on hybrids or comfort bikes. Most club riders are usually roadies, as in they wear the lycra shorts and ride nice road bikes. However, a lot of them are fairly accepting to newbies, you can usually tell that they are if they have a no drop policy but I have encountered some that will drop you the first chance they get. You should note that I live in a suburban area in the midwest so the types of riders you encounter may vary for where you live. Some towns only have 1 club and all the riders are racers who go as fast as they can all the time. Others have only recreational road riders or both types.

The main club in my town has mainly recreational road bikers. Most of them wear lycra and ride road bikes but they usually have limits on how fast they go depending on the ride and they never drop anyone. On my first ride with the local club, I went on the slowest ride available and still found myself falling WAAY behind on my hybrid bike. A couple of riders were nice enough to stay behind and ride with me while the others broke off and went at the pace. After that first ride I stopped riding with them for a couple of months. During that time I started only doing solo rides until I got up to the level I needed to be to keep up. I sold my hybrid and saved up for a road bike and worked up my endurance. By the time I started riding with the club again I was able to do the intermediate rides. I should note, however that I wasn't in very good shape when I started out with the club. Just recently, a guy on a low end hybrid with all Wal-Mart accessories rode with us for the first time and he was able to keep up even on a 25mile windy ride at ~18mph average. So I guess either he was in really good shape or he had a lot of miles under his belt already.

My advice to you is to follow what HiYoSilver said go to your LBS and look for rec rides with "no drop" policies. I would ask club members or other riders to see what speeds the usually average and how far they go per ride, that way you have an idea of what to expect. Usually group rides are a bit easier than solo rides since you can draft people.