I've been in your shoes. Our son's ADHD symptoms became like a neon sign at three and he was kicked out of preschool. We got medical help at age three because his behavior was off-the-charts despite us being good parents.
Charles Barkley is a respected source. Also look at ADDitude magazine and join CHADD.
If you're with Kaiser, they offer a parenting class for parents of kids with ADHD. You need a referral for it, though. Classes are helpful, but honestly, we didn't see any improvement with our son until we started medication. The dots in his brain just didn't connect and we couldn't parent that into improvement through behavioral therapy or parenting classes.
Medication was the best thing we ever did for him. It was an agonizing decision and not something that was presented as an option right away (exhausted everything else) but it was a "WOW!" moment when he went on Ritalin. It's like we finally got to see our real son. Same child, same personality, still full of energy, but with normal behavior. No more attacking people physically, no more spitting at others, no more running across furniture and climbing walls (literally), no more extreme defiance, no more running through circle time. Everything improved dramatically. The downside is that even extended release medication doesn't last all day, so you never fully win over this difficult condition. You still deal with ADHD head-on in the mornings and evenings. And it can take a lot of trial and error to find just the right medication, so your "wow" moment may take a while to materialize.
The AAP just approved diagnosing ADHD as young as four. I can tell you from experience, the doctors CAN help at three if you're persistent (don't downplay your concerns in any way). They can refer you to parenting classes and give advice on managing the behavior problems. You may not have the option of medication until four, but you're not that far off from getting real help.
Be very, very careful about trying diet, vitamin or other "alternative" treatments. So many aren't regulated and many are just plain scams. The best track record with ADHD is medication combined with therapy.
Best of luck!