Ride on the road all you want. All you need to follow by yourself or with a small casual group is whatever rules are legally required and makes you and your group comfortable. Show up for a group ride unless it's specifically marked as newbie friendly and you'll have issues if you don't follow the rules. The rules aren't quite as set in stone as that doc makes them out to be but it's a good introduction to how you're expected to act in a group ride. The rules are just there to keep people from getting hurt. Getting wrapped up with another rider at 30+ on asphalt would really really hurt.