Soil or hydro?...

I would veg for a short period of time...I'd start flowering once the plant vegged to ~4-5 nodes. This way your plant should top out at 3-3.5ft. Go ahead and drill a few holes around the rim of your buckets so you can tie down stems once they get bushy, this way you can maximize yields in small spaces. With that many plants and a 600 be sure to rotate them occasionally so all sides are exposed to the light.

Personally I think ~6-7 females would be perfect for the 600 (VERY good light imo), so if half of those 13 turn out to be males you should be sitting pretty. Best of luck!