I've attached a few links that I believe will give you useful information to your question
Use the DASH Diet to See Results in Just 2 Weeks
Studies Highlight Power of Food to Lower Blood Pressure
Five Foods to Lower Blood Pressure
High Blood Pressure: 9 Steps to Rein in Skyrocketing Numbers
There is also good information on diet and lifestyle changes to lower blood pressure here - http://www.healthcentral.com/high-blood-pressure/treatment.html?ic=4019
You may want to post your question with Health Central Diabetes Experts to see if they would have any further information to guide you from the diabetic aspect.