My bottom line on eating at restaurants is that, for me, it is ALWAYS a discretionary fund expenditure, and NEVER to be accounted for as part of my basic living expense budget.
From my perspective, there is always a prep-it-yourself, frugality-without-sacrifice satisfactory option when it comes to meals. Even when I am traveling. (Hooray for coolers and motel microwaves!).
It also means that, when I decide I want a meal out at a restaurant, frugality is totally optional. The eating out is an "entertainment" event to me, and I pay for it out of discretionary money. So, in such a situation, I consider that smart thriftiness (discount coupon?) is fine; but frugality (refrain from ordering what you really want) is not.