I ride with a groups from two different LBS, one in Scottsdale the other in Phoenix. Each group knows the people in the other and sometimes we ride together, as we did last Friday. The rules, if you want to call them that is everyone must ride with a helmet. We generally ride together, however there are times due to peoples abiliity we get strung out over a block or so. Generally, we ride between 12 to 15 MPH, if the group gets to strung out the lead group will pull up and wait for the rest. We do the best we can to stay together as a group and should there be a problem, the person with the problem is never left to fend for themselve.