Unfortunately, good breakfast food isn't enough to redeem the Liberty Diner. I agree with the reviewers who mention that the Liberty Diner has good breakfast. My Denver omelet was good, the hashbrowns were crisp, just as I had asked, and my daughter said her Belgian waffle and sausage were fine. But good breakfast food only goes so far when there are other major problems.
The exterior of the place was almost enough to make us turn around and go get gas station pizza, but I hoped this was one of those places that looks rough on the outside but is a gem on the inside. It isn't. As others have mentioned, the interior was pretty shabby and could use a good cleaning. I know there is no Missouri law prohibiting smoking in restaurants, but it would be nice if the owners prohibited smoking in their own establishment, as the "non-smoking room," which was completely open to the smoking room, smelled of cigarette smoke.
The server was friendly, but she completely forgot the Belgian waffle part of the Belgian Waffle Meal my daughter ordered. She brought the eggs and sausage and said the waffle was on its way, but we had to ask about it (there were only 3 other tables occupied in the room, so not overly busy), and by the time we got the waffle, the rest of us had finished our meals. The server was apologetic, but it was clear that she and the cook had forgotten about it. The non-breakfast entrees (a cheeseburger and a Monte Cristo sandwich) were fine, although the fries weren't hot, and our cold drinks were never refilled.
In short, the food was fine, the staff needs greater attention to detail, and the owners really need to put some time and money into the building and its cleanliness. If I find myself driving through Mexico, MO again at lunch time, I will not choose to eat here again.