I'm a little older, but in the same height and weight ball park, 5'-2" and started at 244 pounds. I've lost 55 and this morning weighed 189. I started dieting in October, but quit between Thanksgiving and X-mas. I've lost 49 of the 55 since Boxing Day. What I do is strive for a healthy balanced diet and keep my calories below 1500-1600. I follow a pretty simple daily diet really, 3 pieces of fresh fruit, 6-10 servings of vegetables (fresh, broiled or boiled with no added oil or fat), 3-4 servings of low-cal lean proteins (at least one of fat free dairy) and 2 servings of low-cal, low-fat grain based carbs. I eat breakfast, lunch and dinner plus an afternoon snack everyday. Skipping meals always sets me up for a fall because I'll binge in the end.
I also take a pretty hard ride on our elliptical every morning, usually in the neighborhood of 45 minutes. So I think your 30-60 minute walk is on the right track, especially if you push yourself and possibly push a stroller or carry weights. Once or twice a week I hit the gym for a one hour weight lifting session (truthfully I do this sometimes just to get a break from the kids....). I find as long as I keep my calorie intake lower than what I burn by 1000-1500 calories, I'm losing pretty steadily. At this point my diet is going well enough that I'm pretty sure I'll see 120 pounds by Christmas.