First of all, that’s always good to hear. Nobody likes food that tastes like cat food. However, this sign raises some disturbing questions, namely how do they know what can food tastes like? And are they suggesting that other restaurants serve tacos that resemble can food? This is a serious allegation.
Saying “tacos” and “cat food” in the same sentence seems like an odd way to advertise your restaurant, and perhaps they put it there since they know that’s what people expect. Most of these road-side diners aren’t gourmet restaurants, and perhaps they know that customers have gotten accustomed to something.