Steve's template above is a good place to start. Keep it relatively simple to begin with. I have assumed that you can use phpMyAdmin or similar to set up the MySQL tables.
Using your restaurant table as defined above, add a field for UserId. This will allow you to restrict update access to restaurant data
Also consider whether to have a separate field for "Nearest town" and possibly distance from that town centre. In time, this could get more complex by having a table of towns to allow you to select the towns from the table, and then display the restaurants associated with that town. I am building something similar at the moment that you can have a look at if you wish - nothing difficult to do as I am not much of a PHP programmer and my HTML is pretty basic also -
www.archomai.co.uk/ACF (user: guest / password: limited). This is read only, but gives you the idea of what can be done.
For the Menus table:
MenuId (Primary key)
RestaurantId (used to tie menus to retaurants)
Menu Name
StartDate
EndDate
Dishes table:
DishId (Primary key)
RestaurantId (You may want this to be specific to the user rather than the restaurant, but this is the simpler route).
Description
Price
Special (flag whether a special or not - or text to describe when this is available)
MenuDishes table:
MenuDishesId (Primary Key)
MenuId
DishId
Set up the login script (see Steve's tutorial) and consider whether you want account data on the User table for your own purposes e.g. full name, address details, contract length. live flag, etc. This will allow you to restrict people to their own restaurants/menus/dishes through the permissions system - see Steve's notes - but you can add this code later once the rest is working.
Within Dataface, set up the restaurant and dishes tables in conf.ini as the only tables to display in the tables side menu for now.
Then set up relationships.ini files for as described in the "Getting Started with Dataface" tutorial:
Restaurant -> Menus
Menus -> Dishes using MenuDishes
You'll need to use the __sql__ option as you need to restrict the SELECT to the current restaurant only.
Set up formatting instructions using fields.ini files. For instance, I usually hide all the Primary key fields, set bigger text areas than the default, change some of the labels, etc. See the documentation on the fields.ini file.
Hopefully that will help you get started. In time, you may be able to have a single dataface application for edit and view, or you may find it easier to have separate applications.