I know that the hosts can comp food at all three of the downtown properties; not sure about the other Boyd/Coast properties, though (Sam's, Gold Coast, etc.).
There's something odd about some of this though. Last trip, we got our rooms from our host but she said that she could also honor any marketing offers. I got a marketing offer that included $30 food; I was told that I could have a $30 comp for MSS restaurants only, or six $5 vouchers that would be good for either MSS or the Cal (but not the Fremont).
Remember, too, that comps can't be given for Aloha Specialties or Lappert's Ice Cream at the Cal; these are independently operated restaurants that don't belong to Boyd.