Do you need a company specifically knowledgeable in designing websites for restaurants? I guess my advice would be to look at restaurant websites that you like the look of, and find out who designed and developed them.
Also look at different agencies and see what kind of work they have been doing, and whether it matches up.
But, to be honest, unless there's some feature requirements that need a specialist knowledge of restaurants, I don't see why you need someone that is experienced in this exact type of website.
In fact there are many easy to use website building tools that you can use yourself and still get high quality results at a fraction of the price. Especially if you just want a fairly simple website that shows off your location, menu etc..
