I feed my family of 4 on approximately $80 a week. I scan the ads, then I make my menu based on what's on sale. If it's a really good buy (ground turkey - buy 1 get 1 free) then I stock up. My kids (9 and 6) both take lunch everyday. I stock up on the Capri Suns when they are on sale as well as the chips. I primarily shop at Safeway, but I do shop at Costco for larger bulk items and use their coupons as well. My husband and I bring left overs for lunch. I buy fresh fruit and vegetables, milk and juice every week, but I don't care if it's organic or not. I but what is on sale. If organic is cheaper that week, I buy that. I do shop at Trader Joe's on occasion, especially their dessert wine. Whole Foods is too expensive for me and so is Nob Hill.
With a little planning and use of coupons and sales, you will be able to reign in your budget.