Teresa Garcia, weak and in pain, had all but given up on doctors when she came to a small clinic next to a former wedding chapel on the Strip. "I never thought I would get better," the 55-year-old housekeeper said, recalling years of perfunctory physician visits that generated countless prescriptions but did little to slow the dangerous advance of her diabetes. Today, under intense care from a team of social workers, nurses and a doctor who, like her, emigrated from Mexico, Garcia has learned to change her diet and closely monitor her disease. She has regular checkups. She has cut her blood sugar in half. She no longer needs to inject herself with insulin.