Well every baby's schedule is so different, so it really depends. Also you didn't mention if you are working outside the home or not. If you are home during the day, that gives you quite a bit more flexibility. When I had my first baby I liked to work out during his morning nap. My routine was nurse when he first woke up, morning playtime, nurse again, then put him down for a morning nap. That's when I would work out. And then of course try to get showered and dressed by the time the baby woke up. Obviously it doesn't always happen quite that way. Also if the baby is agreeable to the idea, they can always watch you from a swing, bouncy seat, etc. I never went that route but know other moms have. Also I highly suggest getting out and walking for workouts. It does both you and the baby such good to get fresh air and experience the outdoors.
You also asked about your milk being affected by workouts. Mine never was, but I think it depends from person to person. Make sure you are drinking a lot and getting the extra calories needed to maintain your milk supply. Exercising right after nursing always helped my comfort level, but I still have to wear double sports bras for support. Some people say the baby doesn't like the taste of milk after a sweaty workout, but I never experienced that. One thing I've learned about being a mom is every baby is different. I'm pg with #3 and have no idea when I am going to get to work out. I'll just have to wait and figure it out when I meet this new little person.
HTW, Heather