Yes, you can show up and roll with the local club and the non-vintage organized rides that run through the season from early spring to late fall here.
However there is the fun and fellowship part of being with other vintage riders and vintage bikes. I would equate this to the Annual Vintage Car races we have over the 4th of July weekend. While you can go to other car races, this race weekend is all about cars you never thought to see, e.g. the actual Alfa Romeo that Nuvolari drove to beat the Nazi German Mercedes and Audi in the German Grand Prix (and it was raced, I now know what a supercharged strait 8 sounds like), and people who really get the experience, one actually let my wife sit in their monster winged vintage Turbo Porsche with a single turbo charger the size of a basketball (gave true meaning to turbo lag).
It's nice to visit with people and learn about their bikes and in the process learn about your bike. Also there is the issue of vintage versus modern, vintage is a different experience, you only have 5-7 gears, in the rear cassette/freewheel, whereas modern has 10-11, no getting around the ability to keep leg/knee effort in a much broader comfort range with greater gear selection, which with older knees/legs is a real plus, which leads to... You don't want to get dropped, and vintage riding with vintage is going to make that less likely.
So it sounds like the organized rides are few and far between, but you might be able to start a vintage ride with your club, or, post and/or watch for posts in C&V of riders gathering for a ride locally?
Is there a sub-forum for posting rides? Maybe there should be so riders can check a calendar for rides in their region coming up that they could join? Just a thought.