People smile at Jane Juska. There she is, on a rainy afternoon at the Gramercy Tavern in her cheerful red jacket, white hair tucked behind her ears, blue eyes bright behind her bifocals. "I'm agog at the forsythia," she exclaimed, marveling at the enormous arrangements. At 70, she seems to be what she is, a proud new grandma enjoying a day on the town. Though she clutched her lower back periodically