Davd,
Your question is valid; for the amount of Cobras in So Cal (arguably more here probaly anywhere) there really are not that many Cobra get togethers that are pre-planned or listed here. Yes, there are a few, but for as many Cobras in this area the percentage is fairly low I imagine. I take mine to a lot of cruise nights, a lot of shows and drive it a lot - you would think I had the only Cobra in the area. And you are right; it appears that the Nothern California gang seem to be much more active.
No reason just to hang with just Cobras - its cool, but people who share the same pasion are equally fun to hang around with. I joined a local car club and there is nothing like pulling into a cruise night with 30 hot rods all together. Its great. The best listed amount of activities can be seen here. If you are ever in the Fontana area, give me a PM;
http://www.socalcarculture.com/events.html