San Pedro eats late and expensively. Almost everything is on Caracoles, almost everything has adobe walls and a fire, and the prices are the highest in northern Chile — you are paying for the fact that every ingredient came up the road from Calama. The cooking worth seeking out is the cooking that uses what grows here: llama, quinoa, chañar, rica-rica, the potatoes from the villages along the salt flat.
One practical point that matters more than any restaurant: tours to the geysers leave between four and five in the morning, long before any hotel serves breakfast. Know where you are getting food the night before.