Free to peruse the margarines (or what passes for margarine under euphemisms such as "Promise" and "You Can't Tell It's Not Butter"), I am interrupted by a small lady in a red Safeway smock, asking whether she can help. No, no, I'm fine, I tell her. "Can you find what you want?" she ventures again with a big smile. Yes, really.
In fact, help would be welcome, but not the sort of help that any shop assistant, even one with a PhD, could provide. There are a hundred details inscribed on every tub - "no-fat", "lo-fat", nutrient contents running into several decimal points, but none of them tells me what the stuff actually contains. It could be sunflower oil, candle-grease or whale-blubber for all the label says.
At the cereals, where all the boxes are way too big for what is inside, I'm waylaid again. Another Safeway assistant, this time a young man, stops me. "Everything all right?" he asks. "Sure," I say, hoping the "American" reply will send him on his way.
But now I'm at the chaotic fruit and veg stands, contemplating the unwashed potatoes with apprehension - why can't this last word in service economies wash them and pack them in bags? I pick through the courgettes, seeking out the rare unbruised ones. A smallish, oldish man approaches. A big smile: "You find everything?" he asks in almost unintelligible English.
Suppressing the wish to launch a diatribe about the disgraceful quality of vegetables compared with any self-respecting Sainsbury/Tesco/Waitrose, I wonder briefly whether I have not suffered a sudden age-change. So many people want to help.
In mid-worry, though, I am interrupted yet again. From behind the tomatoes, out pops the same red-overalled man, looks into my trolley and then into my eyes (for heaven's sake, is it my perfume, perhaps?) and says he's pleased that I have found the courgettes. Perhaps I'd like some chicken, too? "Fried chicken - very good, better than home-made." I resist the temptation to snap back: "Who says?" and turn to accelerate my shopping before any more of these beaming gargoyles appear. What is this with Safeway?
Now supermarkets in the United States are dangerous places, with ever- fluctuating rules and a frisson of risk, even in genteel north-west Washington. You may get blackballed for taking your trolley to your car, or for not taking it. There is the so-called "social Safeway" in Georgetown where "pick up and go" takes on a whole new meaning of an evening, and there is the "pink Safeway", which is the same only different. And there is always an outside chance you might get caught in a hold-up. But this is Saturday morning, in a leafy family-friendly suburb.
A couple of weeks and a few chance remarks later, all is revealed. I have experienced the arrival in Washington (after a year of cross-country testing) of Safeway's 20-step "superior service" programme, known to detractors as "Smile ... or else". And it turns out the discomfort of customers who recoil from chatty comments on their shopping habits is nothing compared with the torment of staff who find their management-dictated eye-contact smiles misinterpreted.
Inevitably - this is America - Safeway's smile policy is now headed for the courts. A dozen female assistants in California are suing the company, complaining that their smiles have led male customers to try their luck, make lewd remarks, even ask them out. One of the 12, Richelle Roberts, says she was repeatedly propositioned. Another said she was followed to her car.
With the lawsuit awaiting its turn in the courts, the Safeway smile has become a cause celebre: everyone goes to the supermarket and everyone - on the Internet, in newspaper columns and in phone-ins - wants a say, including Safeway staff who just want to be able to turn the smile off once in a while without forfeiting their bonus or their job.
So far, sentiment is running 50-50, with Safeway insisting that its own correspondence is 90 per cent in favour.
At my local branch, though, corporate ardour may be cooling. This weekend, I overheard a young man somewhere behind the organic mushrooms instructing a junior colleague to "remember that smile", but the gargoyle grins are fading. So, if you - as I do - prefer not to make your shopping a communal experience, stop being irritated by that cheery American-style "Have a nice day" when you pass the supermarket check-out. It could have been much, much worse.