yeah if you want to start from bmx, chances are you can probably hold it down a liittle bit from all the standing up and sprinting and whatnot
so if you spend like 1000 on a bike, you'll get all that you need but definitely invest in some decent pedals and stiff clip-in shoes.
if you feel you're up to it, www.bikereg.com,
and you can see where all the races are near you so you can go and watch the pros race and learn a bit. maybe you'll see me there.