'Look, I feel bad . . . I really do. But hey, it's my money. And how do I know what you'll spend it on anyway? . . . I don't . . . Sorry, no money from me.'
The poster, as it turns out, is part of a rather imaginative attempt by New York's underground rail system to rid itself of the city's many beggars - by suggesting to the travelling public that it's OK to ignore their pleadings.
No beggars - or panhandlers, as they are more commonly called here - appeared on my short ride, so maybe the campaign is working.
Back in Washington, the poster keeps coming to mind. Like the subway riders in New York, I also feel irked by the almost constant bombardment of demands for cash by those who somehow feel I must have some to spare.
I am not, however, speaking of panhandlers. My persecutors are more lofty. They include the city's police department, the school that my eldest child attends and, above all, the local public service radio and television stations.
Fund-raising is pursued in America with a zeal surely unsurpassed elsewhere in the world. Part of the explanation lies with the US tax laws that allow you to claim deductions, up to a certain percentage of your income, for donations to registered charities - including, in the case of Bill Clinton, the surrendering of old underwear to the Salvation Army.
Also relevant is the historic unwillingness of the federal government to fund public institutions properly. This was particularly so during the Reagan and Bush years when bodies such as National Public Radio and its TV counterpart, the Public Broadcasting Service, were considered subversive luxuries.
And so it was that last week the main Washington area public radio station, WAMU, was off again on one of its fund-raising drives. It is a twice-yearly ritual that drives everyone I know crazy.
Listening to WAMU in the morning, when it has a news magazine roughly equivalent to Today on Radio 4, is more or less obligatory - at least in this profession. And yet for at least 20 minutes in the hour - and certainly in the run-up to each newscast - we are told repeatedly that the very existence of the station depends on us phoning right away and pledging it bags of money.
As if that were not enough, the local public TV station, WETA, was also looking for dollars last week. The breakfast viewing habits of my three-year-old were completely thrown for a loop. When he was expecting Sesame Street, an announcer appeared and instructed the children to 'bring your parents to the television set for a very important message'.
Happily, my son has already learned how to escape these lectures by remote-surfing to the cartoon channel.
At least the TV and radio can be switched off. Other fund-raising tactics can be more insidious.
The police never give up. Mostly they just call, both at home and in the office, asking for donations for some cause or another that they are involved in. 'Hugs not Drugs' is a current campaign.
Saying no to the police can be difficult. The real danger is that the first time they call - 'Hello, this is the DC Police Department' - you are so relieved to find you are not wanted for some crime that you immediately write a cheque.
Now that is fatal. Once your name is down as a 'giver' you are never left alone (as a colleague on this newspaper can testify).
The police have more tricks. Recently they sent my wife and I two tickets for a ball in Baltimore in aid of a childrens' fund. We never asked for tickets, but the blurb accompanying them made it clear that unless we returned them right away we would be legally obliged to pay for them.
In Britain, we call this inertia selling - don't we? And isn't that illegal?
If you play along, meanwhile, you get a little police department sticker that you are meant to display on your front window, to show that you have contributed. It is hard not to wonder whether houses not displaying the sticker are somehow not given the same protection by the police as those that are.
And then there are the schools. In fairness, my son's kindergarten has been restrained in its demands for cash on top of its normal fees. This is not the case with a school attended by the daughter of a friend.
She complains bitterly of being pressured to make regular extra donations. Her embarrassment is compounded because it is other mothers who make the telephone calls to lobby her.
Last week, when pressed to answer an appeal for cash for a new playground, she replied that she and her husband had discussed it and had decided that they would rather give to more worthy causes, the existing playground being perfectly adequate. The mother on the other end of the call was stunned, apparently.
'Oh, I see,' she said rather brusquely and hung up.
Maybe we all need copies of the subway poster pinned up in our kitchens to help stave off the inevitable rushes of guilt when the answer we inevitably have to give to most of these entreaties is: 'Sorry, no money from me.'