Actually in most cases you can tell the gender right out of the egg, personally I've sexed a 1-2 month old beardie before and it was very easy to see that it was male from just lifting up its tail and looking for either one or two bumps above its vent. One being female and two being male.
I also sexed my two, two year old beardies when they were 6 months of age and they were indeed female and male. Also sexed my sub-adult beardie when she was 4 months and she turned out to indeed be a female, the breeder also sexed her but just to be sure I had a look myself. You just have to get some practice in to get it down, but its fairly easy even for an untrained eye if you know what to look for.