The season starts now. Races till December most places around the country. SS cross is getting bigger -- nice field sizes depending on where you are. Clipless pedals are standard though platforms would work, just not as well.
Turns out that the best cyclocross racer in the world, Sven Nys, started out in BMX.
Races are 30 minutes to an hour depending on what class you are racing. You'll need to practice a couple skills like getting off and getting on the bike without losing momentum.
There are lots of resources out there so have at it. I'd say cross is the best form of bike racing there is.