I don't think there is a certain time of day for exercising. You should do it when you most feel like it and it works for you. If that is a time that fits in your schedule and you feel energized to do your walk for that length of time, go for it!
That should be fine. Whenever you feel it is the best time for you. The only thing I can think of that isn't good to do is a workout with a lot of running or jumping right after you eat or drink alot. You could get a stomach cramp from shaking the food and drink up in your belly.
For me, I can only exercise after light food. So after breakfast, I need one hour before I can weight train or run. After lunch, all exercise is off for at least 5 hours.
So I exercise before food when I can.
If I run on a full belly, I literally sh!t myself.
I agree w/ the above statements. I don't think a brisk walk after an hour of lunch would hurt (unless you have like a 3 course meal). From what I understand, it's actually good to move around after you eat, so you don't get sleepy.