

"No dog's allowed" would seem to imply that the "allowed" belongs to the dog and that there is none of it. Perhaps I should bring my dog there to increase their supply. (Thanks to Kate for spotting this victim of poor apostrophe usage.)
A caveat: Perhaps what this sign is attempting to convey is "no dog is allowed." Although it is an unconventional use of the phrase, I must concede it is possible.
And once again, my office parking lot provides yet another source of mangled English. "Towed at owners expense" doesn't make any sense at all. I plan to use this logic as a defense in court when I get sued for refusing to pay my towing fee.