Leslie Hennessy, owner of Hennessy’s Wines & Specialty Foods in San Francisco, waved his hand over a glass case that sits next to his cash register, across from the deli section where he sells cheeses, gourmet salads and olives.

Inside the case were colorful boxes of Macanudo and Romeo y Julieta cigars. But Mr. Hennessy imagines that the case will soon contain another smokable product  marijuana, packaged attractively because “a rolled up joint in a baggy isn’t going to do it,” he said.

“It would be very similar to the way we sell cigars, where it’s humidity controlled, where it’s under lock and key and there are certain times when it would be sold,” said Mr. Hennessy, 63, who markets his own wine and once led the California Retail Liquor Dealers Association.

Mr. Hennessy said that he had even begun to negotiate prices with marijuana suppliers.

A week before Californians vote on Proposition 19, which would legalize marijuana for recreational use, businesses are preparing to enter what is expected to be a robust retail market if the measure passes. The activity is particularly intense in the Bay Area, where cities like Oakland, San Francisco, Berkeley and Richmond are positioning themselves to take advantage of the burgeoning industry.