Fellow SoCal pony here! I know we have a Central California pony meetup, but they're up in San Jose as I recall, so it's a bit of a hike! I went to a SoCal meetup a year (or two?) ago, and it was a small gathering at a house, it was a ton of fun! But IDK if there's a lot going on here right now, and I find it hard to believe there's not a lot of collectors in our area!
Wondercon just happened last weekend, and although they tout a lot of vintage toy stuff in their booths, there was maybe 2 booths (out of 100!) that had ponies. I know the Frank N Sons swap meet happens regularly, and I found some ponies the one chance I had to go! It was a lot of fun! That's in the LA area, if that's near you!
I think the Rose Bowl flea market sometimes has stuff? I just haven't been personally, becaue I'm pretty far south from LA! But I hope we have more folks chiming in with ideas!