If you're only going to be on travel for a few days, there's no need to prepare any food. Almost any restaurant can serve you rice, pasta, potatoes, and salad. If it's not completely nutritionally-complete, it's not going to hurt you; you'll make up for it when you get back home.
You do, however, want to make sure to get enough calories! Don't make the mistake of trying to live on fruit and salad - these are nutritious, but it's hard to get enough calories to fuel your activities.
You can boost your calories by eating nuts and dried fruit.
“Under the twinkling trees was a table covered with Guatemalan fabric, roses in juice jars, wax rose candles from Tijuana and plates of food — Weetzie's Vegetable Love-Rice, My Secret Agent Lover Man's guacamole, Dirk's homemade pizza, Duck's fig and berry salad and Surfer Surprise Protein Punch, Brandy-Lynn's pink macaroni, Coyote's cornmeal cakes, Ping's mushu plum crepes and Valentine's Jamaican plantain pie."
from Witch Baby, Francesca Lia Block, 1991