The menus aren't online, but food prices are very reasonable.
All the Royals restaurants have kids' prices for burgers, hot dogs, quesadillas, and a few other kids' faves - I think around $3? The various specials are generally half price for kids.
Nightly specials tend to be in the $12-16 range, typically some kind of chicken or fish with rice or potato, vegetable, and soup or salad. About the most expensive thing we've ever gotten is a $23 steak dinner. At the Royal Mayan Palapa, a chicken salad in a half-pineapple shaped like a swan is around $8, and a Mexican platter is around $10-11.
Of course tax and tip and drinks and desserts will increase the cost just as they would stateside. They do not do free soft drink refills. The water is fine - I drink plain ice water there all the time.
There are theme nights - e.g. Mexican Night - buffet + show - can't remember for sure, but I think it's in the $25-30 range including drinks (margaritas or sodas), and half price for kids.
Brunch buffet is around $12 I think - including everything but tip. A big burger or club sandwich is around $6-9, at the restaurants or delivered poolside. At Happy Hour (3-7) the pool and beach waiters will deliver free chips and salsa (you have to ask) with your drinks. My kids get alcohol-free strawberry daiquiris, pina coladas, or chocolate monkeys for around $1, and I think a beer at happy hour is $2 - plus tip.
The Express take out - at the Royal Caribbean, Sands, and Haciendas, take-out or free delivery (tip of course) is a great option. Ribs are about $13 (I think it's about 1.5 racks), a good sized roast chicken is $7, a quart of soup (black bean or mexican lime) is about $4, a large caesar salad (to share) is about $4. A large pizza is around $12 I think.
A whole key lime pie at the express is about $8. A tub of ice cream in the mini markets is around $4-5. In comparison, ordering dessert in the restaurants will be around $4-5 per piece of pie or cake, and a Hagen-Dazs ice cream cone or bar will be around $4 in the mini-market.
Mini-market sodas and beer are about $1 per can. Cereals are around $2-4 per box.
I think we spend less there than at home.
Please post again or PM me if you are thinking of any particular types of food.