The food is pretty rough, I would advise to stock up on biscuits and crisps b4 leaving the uk. Although the food in the restuarants is good and cheap, so consider eating out
Depends what you're used to and what your expectations are, really. In the Rila we found the food to be a bit school-dinnerish, but always edible, plentiful and filling. We always found something on the buffet that the kids would eat. I have certainly come across worse, but if you want gourmet food, look elsewhere.
G~.