well if youre keeping them together, youll see it sooner then later. bulges can drop anywhere from 6 months to a year, and usually happen after they hit 10-15g. an easier way to sex is by the rows of preanal pores above the cloacal lip between the legs, males will have a few rows of dark pitted pores, and females will lack them.
here are pics:
adult male ciliatus

adult female ciliatus
this is what the pores on a juvenile will look like:
male

female
if theyre both females you can keep them together, if theyre both males, youll need to seperate them when they show signs of agression, and if you have a pair, youll need to seperate them at about 20g, so the female isnt bred too early, which can be detrimental on a growing animal, if not fatal.