Well that's really, really obvious- Race CVMA!
No really though, Chuckwalla is probably my favorite track down here, and it's great either direction (although I maintain that CCW is still better). The surface is still smooth and grippy, it's challenging, and it's pretty decently fast, but still technical enough that you're not necessarily going to be a sitting duck for anyone who has a horse stable with a few more cubic centimeters. The only downsides to chuckwalla are the weather, as it tends to be really unliveably hot during the summer, and the complete lack of amenities, as it's in the middle of BFE and still being built up. But the track and the people who run it are all fantastic, so that would be my number one recommendation.
But if for some reason you don't want to do CVMA (ludicrous that I'm even entertaining this scenario, I know), Streets of Willow at Willow Springs is well suited for the 250, as it's tight and technical with pretty minimal horsepower sections. And if you're really ambitious and a man of last minute "throw all your **** in the truck and go!!!" then you can come down and actually race there THIS WEEKEND
I wouldn't say it flows quite as nicely as Sears Point does, but it's very much so a physically exhausting track, as you very rarely get a moment to be straight up and down.
Otherwise, we have Auto Club Speedway (aka AAA Speedway, aka California Speedway, aka Fontucky), which is a Nascar track and thus is in the middle of everywhere and has great amenities. But while I've only been there once, I didn't really care for it. The heavily banked front straight is fun, and it's got a few sections I enjoyed, but it just seemed like a lot of long straights connecting tight corners so it was a constant game of recovery. Maybe it's better than I remember, but it costs way too much to be worth a second go for just a trackday to me.
Then there's Big Willow also at WSIR, which you are literally pinned a majority of the track. It's only 9 turns and most are quite fast and wide, so it's not a particularly challenging course on the 250. I actually enjoy it in it's own right just because it's such a different experience and isn't terribly difficult, but I wouldn't really say it's worth travelling much more than the 80 miles or so that I do for that one.
And well, you've already been to Buttonwillow, so that's old news.
And I think that's it for SoCal, unless there's still a track down here somewhere that I've never been to or am inconveniently forgetting off the top of my head. So basically, in conclusion, COME DOWN AND RACE CVMA!
