Sam, check with your local bike shops. Many of them have weekly rides. The problem is that many of them may be racing training, although that season is over for now. Check to see if there are groups that do the BAK. I know the Santa Fe Bike shop in Leavenworth has quite a group going. That’s the wrong direction for you, but the principle will be the same.
I NEVER train for RAGBRAI. Training is such an ugly word and sounds too much like exercise! I do ride a lot! Now THAT’S fun!! So far I’m at about 3700 miles on the year. That’s short of my goal, but oh well!