Food in Bukit Lawang is cheap and mostly Indonesian, with a strong tourist slant — guesthouses and small warungs serve nasi goreng, mie goreng, gado-gado, and banana pancakes with equal confidence. The better places have a view of the river; eating on a terrace above the Bohorok while macaques eye your plate is a reasonable summary of the Bukit Lawang dining experience.
Prices are well below what you'd pay in Medan. A full meal rarely costs more than 30,000–50,000 IDR.