I ride almost always by myself. The exception is the time I spend riding with my teen age daughter, but that's probably 1% of my overall riding. Though there are several organized groups in San Diego (the Knickerbikers being the most well known) I've just never gotten into that. I suppose I like the freedom and flexibility of solo riding -- but I bet I would also like the companionship of groups.
Anyway, I thought I'd run a little poll to see how 50+ers ride. Please check the option that's closest to your style of riding.