I would say about 100-150 dollars. That's how much i useally spend on my groceries a month. I spend $1300 to $1500 for a family of 4 (kids 6 and 10 yrs) plus about $300 in restaurants.
This varies widely based on the area, type of restaurant, and time of day. Lunch menus tend to be cheaper, as do local joints compared with national chains. But for dinner at Applebees, I'd say 30-40...