It looks like the GR2R ride is designed for newbies.

Suggested Preparation | Cascade Bicycle Club

So, if you can ride... go have some fun. You may want a road bike, but there are quite a few to be had on a budget (do you fit?)

I haven't done a lot of group rides, but two weeks ago I went out on one of the local GEARS rides here in Eugene (12-16 mph, hilly). About 8 people showed up. And, it was fun. A few hills... there are also flatter rides if one wishes. Several stops to regroup. Technically it was a no-drop ride.

I'm pretty sure I had the oldest bike in the group by a few decades. Out of the 8 people or so that showed up, I don't think there were 2 bikes that were the same brand, including 2 classic steel bikes (mine, and an old Peugeot), a Litespeed, Motobecane (new), Specialized Roubaix, Trek???, and a couple other brands.