Does statin really elevates risk for diabetes? How could one know whether it is safe to take statin if there is no obvious risk factor for diabetes?

Controversial. Some studies have shown a higher incidence of diabetes in patients on statins, which appears to be dose dependent (higher doses may confer higher risk). This may just be because the people who need higher doses of statins may be more likely to develop diabetes, rather than the medicine causing diabetes. I would take it if recommended by your doc and try to follow a healthy lifestyle!
Some do, not all. But benefit in reducing heart disease 40-50% has caused cardiologists, endocrinologists to accept tiny risk of causing diabetes (2 in 500 patients, raising sugars mildlyin those already diabetic and prescibe statins pravastatin less likely to do it.