I broke mine when I was about 8 years old.  I tried jumping down some stairs, didn't stick the landing, first thing to break my fall was my hand...snap...broken wrist.
There's a chance you'll have a cast that keeps your arm at a 90 degree angle with your elbow, and the cast will go above your elbow and down to the second set of knuckles.  It really depends on the severity of the break and how far up the wrist it is.
As far how long you have to wait before you get a cast, that depends upon how bad the swelling is.  The longer the swelling persists, the longer you have to wait to get the cast.
Casts aren't really that bad.  I broke my hand in football my freshman year and had a cast that went from the second set of kuckles up to my elbow, I still managed to play Offensive tackle and defensive tackle with it on.  Just had to wrap it up so that I didn't hurt anybody with it 
 
Worse part is when you get the cast off, your arm will be half the size as the other one, the hair on it will be really black, and your skin will be all icky.
Just something you have to deal with :frown: