Whilst rereading Harry Potter and the Philosopher's Stone, I came across this curious passage:
The people hurrying by didn't glance at it. Their eyes slid from the big book shop on one side to the record shop on the other as if they couldn't see the Leaky Cauldron at all. In fact, Harry had the most peculiar feeling that only he and Hagrid could see it. Before he could mention this, Hagrid had steered him inside.
To me, this suggests that, like Hogwarts, the Leaky Cauldron is magically concealed to look uninviting to muggles, perhaps even a closed down pub. It certainly would make sense that it would be concealed to Muggles, but is there any evidence to support this theory?