Diabetics often have lower recommendations for blood pressure, the maximum normal value being seen as 130/80-85. However, it’s questionable whether it’s a good idea to medicate your blood pressure levels down to those values. Diabetics can probably stick to approximately the same upper limit as people with heart disease: 140/90 (according to new studies and expert comments, as well as the latest recommendations from the American Diabetes Association, ADA).
There are many good options when it comes to such medication. Examples are ACE (angiotensin-converting-enzyme) inhibitors or AII-blockers (angiotensin II receptor blockers) such as Enalapril or Losartan. If this kind of medication doesn’t give the desired effect, you might have to add other medication such as so-called calcium antagonists (e.g. Felodipin) or a mild diuretic (can be found as a combined pill with Enalapril and Losartan).