I was blowing between $6-$15/day on lunch at work. I nipped that in the bud by packing what my coworkers call my Hungry-Mans Lunchable.
One day I will take a pack of honey ham sliced sandwich meat, a block of cheddar cheese, a tube of club crackers, some Frito's, either grapes or pealed grapefruit, a glass of milk and 4 chips ahoy cookies.
The next day will be peanut butter and jelly stored in small separate containers, 4 slices of bread or club crackers, Lay's BBQ potato chips, either a banana or apple, a glass of milk and 4 chips ahoy cookies.
Then I'll take a bowl of Smart Start cereal, a can of peaches and 4 chips ahoy cookies. Don't forget the milk.
I got lunch down to under $2/day now. When you shop for your lunch box pick the one that seems to be the right size and buy the next bigger size. I have a pack of blue ice that I have been using for a few years now.
I'm envious that you will find a nice park or road side picnic bench to enjoy your lunch. I have to eat at my desk :(