If you are free on Wednesdays, I have the group for you! The Wednesday Wheelers are part of CRW. We mostly ride in the NW suburbs, with occasional trips to the north shore, Cape, etc. The rolling average is about 13.5. Many times the ride is split into 2-3 groups, where the fastest group has an average of 15 over hilly terrain. There are some who want slower than 13.5, too. We use a human arrowing system. While sometimes I get a little frustrated with the group, these are for the most part *very serious* athletes, some who have slowed down, others who just want to ride at this speed and socialize. It is not a group for beginners by any means. If you want to get on the email list, PM me and I will send you the contact name.
You would also be perfect for the AMC Thursday night ride series. Go to Outdoors.org and you can look up where the rides are each week. I am a leader for AMC, and you would be perfect for the rides my DH and I lead. AMC rides are social and not like typical bike clubs. We have our characters, but it's fun.
And finally, you sound like you would be a good match for riding with me. When I work hard, my average is around 15.5, but throw in some hills in Harvard and/or 50-60 miles, go down accordingly! I don't do lots of group rides, even though I am a leader and tend to ride with my husband and one other couple. Let me know.
2015 Trek Silque SSL
Specialized Oura
2011 Guru Praemio
Specialized Oura
2017 Specialized Ariel Sport