VERSOIX, Switzerland (AP) _ A lone customer drove up in front of Denner's discount store. ''You have only two minutes to do your shopping,'' warned a uniformed policeman. The man drove off again, shaking his head.

Shops and restaurants emptied Tuesday all along the Route de Suisse, the road from Geneva to this little town were the superpower leaders met for the first time in a lakeside mansion.

A leather-capped Soviet plainclothesman, shivering in his raincoat, stood in front of the villa Fleur d'Eau's wrought-iron gate. The language barrier made impossible any chat with the Swiss police officers also posted outside the walls.

When the two leaders arrived for their first round of talks, their motorcades traveled a road barren of traffic but lined with hundreds of Swiss police and no-parking signs.

All cars have been barred from the road, and a truck with a triangular sign indicating a breakdown prompted suspicious looks from the police.

But the Cafe de La Frontiere, a truckstop about 150 yards from the summit villa, was as crowded as on any workday and comments on the summit events flowed as freely as any discussion of soccer.

''It won't be of any use,'' said Jean-Pierre Magnin, 25, a truck driver.

''They're making quite a big fuss over this,'' said Georges Bastien as he polished off a plate of tripe Milanese. ''But it brings in dough, doesn't it?'' he added.

''Why shouldn't they meet?,'' asked Gilbert Thierry, another truck driver who joined in the conversation from a neighboring table. ''Maybe it helps.'' His co-driver, Gilbert Dellay, registered doubts. ''I think both have pretty rigid positions.''

''The radio said Reagan arrived 13 minutes ahead of schedule,'' Thierry said. ''Didn't they both get good Swiss watches?'' he joked.

At a corner, Jean-Pierre Kiener was emptying his glass of Beaujolais. ''It's a great show. I don't think that much will come out of this,'' he added.

Simone Nerfin, the 79-year-old owner whose family has run the cafe for more than a century, was more upbeat. ''Let's hope they will agree on something good,'' she said.

Francis Oberson - the only client sporting a tie - was the only outsider at the cafe, along with his Italian-born wife.

''We just dropped in here because it's close to the summit site,'' he said. ''We saw both of them this noon, and we will watch them again arriving for the afternoon session. Both made a good impression, but Gorbachev seemed a little tense.''

''I think this summit is a good thing,'' Oberson added. ''They should meet more often, keep in touch, yes, that would be good for world peace.''