Yes, Moco Maffia, Montgomery County part of DC Tri Club, always has good rides each weekend. They have a FB page for more information.
Here is the link: https://www.facebook.com/groups/220603631479498/
As for spin classes, it is my recommendation that you do NOT do spin classes even if they are lead by a cyclist. Why? You are not fit for the bike and as you begin to fatigue from the volume of training, this drastically increases your risk for injury (which is already high for the IM distance).
If you are traveling or you actually take your bike and trainer to the class, it is my recommendation that you pass on this option for at least the next 6 months. Sorry!