Hi R..
I did the South Beach Diet two years ago after my first baby was born. She was six months old and I was finished with breastfeeding, so I was definitley ready for the pounds to come off by then! I lost 11 pounds in the first two weeks, and another four in the six weeks to follow. I would suggest buying the book and reading it through. It will give you a really good idea of what the diet is all about. It is a VERY well balanced diet and the strictest part is only two weeks long. I bought the South Beach Diet 30 Minute cookbook too, and I use that to plan out meals in advance. I actually end up saving money at the grocery store because I have started planning meals in order to make the diet easier to stick with.
Here's a note about something another mom said about the diet: It's not very often that you eat or use artifical sweeteners. Sweeteners aren't gas-causers. I did have to run out and buy gas-x the first week I was on the diet because of all the vegetables/fiber I was eating. It was actually a good thing. My body wasn't used to all those veggies! Most people get gassy with a lot of fiber.
I am currently doing the diet again, though I am breastfeeding, so the weight isn't dropping off like it did the first time. If you are breastfeeding it's suggested you start with phase two of the diet. It is also said that the diet is the most effective the first time you do it. Even if you just adopt some of the principles from the diet after you've lost the weight, then you shouldn't have a problem keeping the weight off.
I hope this helps. Let me know if you have any more questions.
J.