I agree with finding a group ride/shop ride/ club, or something where you can ride with experienced riders before you consider racing. It's not like running.
Definitely don't invest in a bike that doesn't fit. A Cannondale CAAD would be a decent starter bike which can be raced. You're going to have to figure out what size you need first.
As far as downhill speed, some people never get comfortable with it and that's ok. Some go crazy before they have the skill or brains to handle speed.