You might lose weight quickly the first week, or you might not. It's hard to tell. Since you've been dieting anyway, you probably don't have a lot of excess water to drop, which accounts for a good portion of the initial weight loss for any diet. BUT the fat comes off at a nice steady rate, and most people feel really good on the plan
Do you have the book? You'll definitely need it, though you can find a lot of helpful info including food lists in our South Beach FAQ forum.
Good luck!