While he waits for the new season of “Mad Men” to start shooting, John Slattery has some time on his hands. So the silver-haired actor who plays Roger Sterling on the hit AMC show was in town Wednesday to attend a party organized by Boston Common magazine. (A Newton native, Slattery appears on the cover of the current issue.) Slattery, who had lunch at Legal Sea Foods in Park Square, swears he’s nothing like the cunning ad man he plays on the show, but he’s certainly just as handsome, showing up at the Smith & Wollensky on Atlantic Wharf looking rested and wearing an exceptionally well-tailored blue suit and white shirt. He was joined at the party by his wife, Talia Balsam , and their son Harry, who was apparently bummed because he was on the red carpet and not at the Red Sox game. Asked about the Sox, the optimistic actor predicted they’ll “hang around until the end of August and then pick it up.” With the show on hiatus, Slattery seemed focused on enjoying the summer. He said he’ll spend July 4 at his sister’s place in Scituate and a few weeks in the Hamptons. After that, it’s back to work. How does he manage to remain sober with as many martinis as Roger Sterling swills every episode? “I’m drinking water with onions,” he said. “It’s 6 a.m. No, we’re not really drinking booze. But I’m glad you think we are.” The crowd included Boston Common brass Glen Kelley and Janice O’Leary , Davios owner Steve DiFillippo, chef Marc Orfaly , “Baywatch” beauty Tracy Bingham, realtor Beth Dickerson, Clear Channel’s Mary Menna , and WGBH’s Jared Bowen.