Several times per week (once a week we eat Subway). The other time we do various things i.e. sit down restaurants, places we've never eaten at before, old favorites, that type of thing.
I usually eat fast food once a week. Sometimes advertising will affect my choice of where to eat, but I usually just go to my favorite fast food restaurants. Wendy's is my favorite and their new Frosty ads make me like it even more.