They're your words, choose them
You've seen the signs:
ABSOLUTELY NO CREDIT CARDS.
NOT RESPONSIBLE FOR LOST OR STOLEN ITEMS.
BATHROOMS FOR PATRONS ONLY.
Guess what? There's no legal requirement that signs have to make you sound like a harsh jerk in order to carry weight or to inform the public.
To keep our prices as low as possible, we only accept cash. The good news is that there's an ATM next door.
Careful! We'd like to watch your stuff for you, but we're busy making coffee.
Our spotlessly clean restrooms are for our beloved customers only, so come on in and buy something! Also, there's a public bathroom in the library down the street.
In fact, you might find that when you speak clearly and with respect, you not only communicate more effectively, but people are less likely to blame you when something goes wrong.