I do find that signs with grammatical mistakes annoy me, as do those which are garbled and incoherent. Signs normally only contain a few words, so it is surely worth checking them before they are printed.
I have seen questions raised about the correct name for the symbol @ many times, often suggesting that it has no name:
Email, with its address template [email protected], is virtually universal. Nevertheless, the @ that unequivocally marks it as an email address has no generally accepted English name. (Julian Burnside)