Was going to suggest TJ's but somebody beat me to it. Yes, Trader Joes sells great, cheap mostly cooked stuff that I've relied upon for even business trips. I just hate ingesting restaurant food that frequently.
Breakfast - you can buy granola or cereal and have it just plain or buy small container of milk or yogurt and put it in the fridge, pre-cooked eggs, fruits etc.
Lunch - I love a nice big salad for lunch, especially this time of the year when things are warming up. I usually pick up a bag or two of salad greens, along with precut veggies from TJs like radishes, beets, carrots or their four veggie blend with carrot sticks, celery, cherry tomatos etc. are just fine also. Along with this I pick up a can or two of beans (chickpeas, black or pinto), may be a couple of avocados and some salad dressing (I like their greek or ranch), may be a block or less of cheese (or grated if you prefer those instead). And some red wine because I like to drink wine with lunch sometimes. :)
Edited to add: I can usually get the above for under $35, which keeps two people (me and spouse) going for about 3-4 days. Rinse and repeat. Toss in an occasional restaurant meal.
Dinner - repeat of lunch. I also pick up a few canned soups (or their packaged tomato/butternut squash etc), a loaf of bread and something to put on bread (like hummus). Pick out their taco shells if you want to make it fancier. Another glass of red wine if you fancy. :)
Occasionally pick up some dark chocolate, and some nuts for snacking. Along with whatever fruit you like. I usually do ones that don't require washing/cutting like bananas, apples, oranges, or precut ones like watermelons and pineapples.
I do this regardless of the town I go to as long as there's a TJ's there, because their products seem to have internal consistency, and the pricing is the same across all cities. Plus I don't have to wade through aisles upon aisles with so many different branded stuff - I can also mostly ignore reading labels because they carry mostly clean stuff, plus you are restricting your diet to mostly natural stuff anyway.