I imagine that I will be growing my own vegetables in planter boxes either outside my window or in my yard (if I'm lucky enough to have one). If I am living in California at that time, I will be able to grow some berries or fruits (space permitting). The grains and protein for my meals will come from local farmers and farmers markets in the area. Eating locally and organically (and maybe even vegetarian!) will hopefully become the status quo throughout the USA since it supports the local economy and significantly reduces our individual carbon footprints.
Luckily, local and organic foods found at farmers markets are generally affordable and can be both good for your health, carbon footprint, and budget.
Don't forget to reduce your consumption of meat! It takes 2,607 gallons of water to put a steak on your table but only 3 gallons for a tomato.