Widdle Guy, that's great to do what you can naturally to try to control both your diabetes and blood pressure. 138/70 is not a bad pressure at all, but if you see that your BP is consistently above 150/90, then you really have to do something a little more drastic.
Exercise is a key factor for both problems and can contribute to keeping the numbers down. Smoking and drinking alcohol greatly affect blood pressure, and of course, alcohol affects diabetes - great source of SUGAR! Controlling stress is a major intervention to high blood pressure, and also controlling weight (I don't know if that applies to you, but it sure does to me!).
It's not always true that once you begin a medication for blood pressure that you will always have to be on it. It is true in most cases, but I have seen people come off the meds, too, so depending on how well you work at controlling the other things, you might not be on it forever. One thing for sure I do know, you don't want to have a stroke or heart attack, which is certainly a possibility with uncontrolled high blood pressure, and especially with the added problem of diabetes.
You might want to check out this site:
Hope it will be helpful!