Last trip in November, we were 3 adults and one child (8 yr old). Including our travel days (we drove from NJ), we averaged under $17/person/day for all meals and snacks. We ate breakfast in our condo with food purchased at the supermarket. We did counter service, a couple of buffets, some offsite meals, some sit-down - a nice variety. Thanks to the obscenely large portions at most restaurants, we often shared meals which helped lower costs. We also drank mostly tap water or 3 of us shared one soda when we got one.
I've seen plenty of people say they spend upwards of $50/person/day, so the range varies a lot, but there is no need to spend a fortune on food unless you really want to.
Steve