Probably closer to 13 or 14 weeks, I don't remember exactly.
And no, it was not enjoyable. Not really. It didn't hurt, but it didn't feel good either. And I had 2 c-sections, so I wasn't dealing with tears or stitches. But if your wife is breastfeeding, keep in mind that her hormones are still wacked out and she is going to be a lot drier than usual.
For me though - it was the sleep deprivation, the stress, and just wanting two freaking seconds to myself that made sex so unappealing. I would spend the entire day and most of the night holding and nursing a baby, I was exhausted and just sick of being touched, I wanted to be left alone.
If your wife feels that way, don't take it personally. But know that giving her as many breaks as you can, holding the baby so that she can take a long hot shower, sit by herself and check her email, even just take a 20 minute catnap by herself.......those things will go a LONG way towards making her feel up for sex.