Advertising guru and Hamptons fixture Jerry Della Femina is sharing his lowbrow foodie secrets for those heading east this weekend. “When you are stuck on the Long Island Expressway, you have to have a goal,” he says in the new issue of the Daily Summer. “Mine is a sausage Egg McMuffin in Manorville . . . It has everything that Mayor Bloomberg says is bad for you. Everything that he says is bad, I go after as fast as possible.” Della Femina’s obsession with the breakfast treat isn’t exclusive to the Hamptons. “I have had it all over the country,” he shares. “I have my phone set up so I can click and find the closest McDonald’s.” The Madison Avenue legend, 76 — who’s been called “Peggy Olson, Don Draper and Bert Cooper rolled into one” — says he misses the “Mad Men” era of the swinging ’60s. “There was the smell of grass in the office almost all the time,” he recalls. “I used to always encourage people to get involved with each other sexually because they would get in to work earlier and leave later,” but, “Human Resources destroyed the world.”