Most of mine have showed about 5 weeks in. Some Kush that I have vegging now is on it's 5th week and no signs of puberty yet. I think at the worst most strains will show before 8 weeks. I had some show on there 3rd and 4th week also.
yeah like str8drop said usually around the 5th week bt it depnds on strain mainly, bt sexing can be accomplished thru a week, maybe 2weeks of 12/12 light bt if u growing outdoor then its just a waiting game.
Jah Bless and good luck.