what count do most people throw their curveball on??

There really isn't much of an answer for it.. Depends on the pitcher, and how well you can control your curve, relative to your FB and anything else you may throw

You can mix it up, and throw a first pitch curve, or throw it 2-1 to give someone a different look

Throw it as a strikeout pitch, or be selfish and go with a high heat..

You can throw it any count if you can control it
But my suggestion is
0-0 =to show something other then a first pitch FD
and anything ahead 0-2, 1-2...

I throw it in any count, except 3-0 and 2-0 because I know I can control it, the other day I got 2 guys looking at 3-2 curves, its all about if you feel like you can throw it for a strike.