You may see your female licking the trail where the joey's will crawl to her pouch. If you see them born it will be a small pink blob. Other than that, like moorie said, a few weeks.
I thought since we were talking about joey's I would share that mine are almost OOP. I woke up this morning with a horrible stench in my room. It is from the stuff draining out of the pouch. It's just the mom passing it thruogh her system, so hopfully in a few days I will have two healthy joey's. I remember this smell from last time, when she goes to the bathroom it is dreadful.