I think it took me just a few days to learn to ride confidently with clipless pedals. At first i rode noob style clipping out quite early before the stop. Only fell down once clipped in and that was because i got stuck in sand. But clipping out early means one has to anticipate traffic conditions. And you can always clip back in if you don't have to stop afterall.

Nowdays i wait till i trackstand in traffic lights before clipping out. You can always tell a riders experience and confidence level by the speed in which they clip out. Good riders clip out after stopping. Noobs clip out 100 feet before the stop. But that's ok, because everyone was a noob at some point. And only experience makes better.