It's not that Miami Bunny Carol Vitale isn't keeping her options open. After all, she did take a leave of absence from her Playboy duties last summer to sing at a friend's night club in Glens Falls, New York. And her application for a job with the public-relations department of a major airline was accepted. It's just that when it came time to decide whether she wanted to trade the endless summer of Miami and the friendships she's made and the advantages she's accrued while working at Playboy for another kind of life, well, let's simply say that the skies she'd been so attracted to previously didn't seem that friendly anymore. "I was all set," says Carol, "to take my first airline training class. But I couldn't take my mind off how much I'd miss Playboy and all my free time for modeling assignments, guitar lessons, water-skiing and the rest. For me, living in Miami is like being on vacation every day of the year, and I kept on thinking about how much I'd be away even if I ...