I would say at least a year... it takes at least that long for your body to fully heal (this is way many OB/GYNs say to wait a year before trying to get pregnant, your body has lost so much vitamins, minerals and so on from the growth and birth of a child that it takes at least a year to regain everything).
Go for the yoga, seems like a class devouted to postpartum and I hope it helps you. If you find that you still have aches and pain after a year maybe looking into having a chiropractor or another doctor give you a good check over to see if they can pin point the aches and pains. This way you can focus on those areas with certain stretching and strengthening exercises.
For me it took about two years to feel back to my "normal" but I also struggled with depression for a year and a half after... so that did not help with trying to figure out my other physical ache and pains.