Where in California are you? The Atwater near Los Angeles or the Atwater near San Francisco? Both are within driving distance for me if you are going to have a nice big event. Southern California is full of 1/8 tracks. You should check out this racing series and maybe contact some of the owners for help: http://www.jimmybabcock.com/ There are some great pictures of the tracks on this site as well.

I'm no dirt expert. There are several tracks in Southern California, and I find that none of them have similar racing surfaces. I like them all for all kinds of different reasons. IMO, you can't go too wrong with whatever you decide to use. Thunder Alley is the only one that has a lot of clay. They water the track for most of their events.

I personally don't like it when tracks add stuff to make the surface bluegroove. If it were me, I would just run it wet or dry. I raced on a track just recently that used something on the surface, and ran it dry all day. Look at what it did to a lot of the metal on my car (picture below). It looks like I took a trip down to the beach, lol. I'm not sure what they used but I've never seen this happen before. Also, here is a picture of what my local track did at their last big event (picture 2-5). Talk about bluegroove. I'm not sure what they used either; it was environmentally friendly though. I do like it when they use it for the dirt oval, but that's it. It's a tire killer.

A nice shade for the drivers stand is a must. I like Thunder Alley's (picture 6-7).

I like the AMB system. Just about everyone I know owns a personal transponder, although you can have handouts as well.

I dislike crossover jumps or multiple lanes. Just make the whole track one lane, and see who's fastest.

If you wanted to be really cool, make another drivers stand specifically for video, photographing, or for spectators as long as it doesn't get crowded; maybe devide it up. That would be world class. I saw they had that at the Farm II for the IFMAR Worlds. My local track has another drivers stand from the track they tore down. It's pretty cool.