"Eat lightly and drink alcohol prudently when you begin your vacation."
That wise advice comes from an experienced travel guide who reinforced what I already know.
He went on to explain that people get carried away in a new location and go full-out forgetting that in the case of their stomachs, it takes time to adjust.
Likewise, water is essential for hydration, and especially in warmer climates. Bottled water is often the safest route in certain countries, too. Hibiscus tea- hot or iced - with a small amount of maple syrup helps, as well, to replenish the body with important nutrients.
A carton of local yogurt for breakfast gets your body acclimated to different types of foods than you normally eat at home.
My suggestion is to stay away from green salads, and select fresh fruit instead from a hotel buffet table when traveling internationally. Use your own judgment here in the United States.
Street food is another matter. There are pros and cons, and the more experienced you are traveling, the better you will be able to consider all the factors. There is no single definitive answer. I've seen people so careful in their eating habits get gastrointenstinal ailments that put them on their backs out of commission. Likewise, I've seen people very free in their eating never get a stomach ache. Go figure.
When I eat locally grown foods when I am traveling, I find that my body is satisfied.
A vacation is not the time to be stringent on your diet. Go out and have fun with food.