I heard of a way to sex a plant before putting it in the ground. I've never done it so others might want to chime in to confirm this can actually be done...but its what I'm planning on trying when the time comes.
You need to have access to lights to force flower though. What you do is take a clone and as soon as its established, force flower and you can tell the sex then. That IS possible right?
Cheers,
Phrasty