At least 150 minutes per week of moderate-intensity exercise or Ninety minutes per week of vigorous-intensity cardio respiratory exercise. Thats the amount recommended by the American Heart Association (AHA) for reducing cardiovascular risk in people with Type 2 diabetes, according to a scientific statement published online on June 8, 2009 in Circulation. Both the options are considered minimums, according to the document, from a writing group chaired by Dr Thomas H Marwick (University of Queensland School of Medicine, Brisbane, Australia). In addition, "moderate- to high-intensity" resistance training three times per week is highly recommended.
The document is rich with evidence from the literature to support the recommendations, but "unfortunately, only a few large-scale, randomized, controlled trials are available." In addition to moderate and vigorous exercise, patients should be encouraged to perform resistance training 3 times per week. Resistance training should use all muscle groups and progress to 8 to 10 repetitions per set for 3 sets of exercise.

          Exercise results in improvements in insulin sensitivity and vascular function. Patients, who start out de conditioned or are limited by co morbidities, can begin lightly and work their way up to the training goals.

Source
Marwick TH, Hordern MD, Miller T, et al. Exercise training for Type 2 diabetes mellitus. Impact on cardiovascular risk. A scientific statement from the American Heart Association. Circulation 2009; DOI: 10.1161/CIRCULATIONAHA.109.192521, available at: http://circ.ahajournals.org.