Hey,
I just moved from Fresno a few months ago. Lived there for 5 years. There are a few MX tracks nearby, but none in Fresno. Hanford Cycle Park, and the Madera Fairgrounds are the two closest. Not sure what kind of series they have. Hanford is your best bet, though, as I rarely saw anyone riding the track at the Madera Fairgrounds (I drove by it a lot when I was commuting).
But if you're at all into trail riding, there's some of the best riding in CA only an hour north, right near Yosemite. It's called Miami Creek. There's about 80 miles of singletrack & fire roads. I miss it, but still have riding buddies there & plan on hitting it a few times a year. And for some reason, there's hardly ever anyone there. I love that place.
There's a Honda/Yamaha/Kawasaki/Suzuki dealer in Fresno, Clawson Honda, and they're much like any other dealer. They'll have info on the local MX series. There's also a kTm/Yamaha/Kawasaki dealer, Wilsons, they're a little less desireable. Then there's a Cycle Gear store. Thats where I got all my stuff that wasn't worth mail ordering. And they're pretty nice there.
If you have any questions about the area, give me a holler.