Sitting at a lunch restaurant where one can order either from self service kiosks, or from a person behind the counter. The counter has a handwritten sign "cash only at register".

Now, which meaning do you think that they intended? That if I want to pay in cash, I have to go to the counter? That if I walk up to the counter, I have to pay in cash?

(Yes, I could have asked, but by the time I spotted the sign, there wasn't anyone by the counter, and I had already successfully used the self service kiosk).

...and asks the bartender for the WiFi password.

The bartender replies, "you need to buy a beer first."

So the guy buys a beer, and asks again, "what's the WiFi password?"

The bartender replies, "you need to buy a beer first, all lowercase, no spaces or punctuation"