It's true that race attendance varies during the year. There is no such thing as a bad race at El Mirage.
Last June there were 111 entries, 70 cars, 41 bikes. Everyone had an opportunity to run twice. There were 172 runs.
Fastest race speeds are in the mid 250's (WOW). Race starts are by points position, so the fastest run first. Make sure you are there at sunrise. You can wander anywhere at the pits and drool admire all the cars and bikes.
Once you get to the lake bed don't expect much. All the activity is at the other end and you have to drive quite a while before you see anything.