Developing hypertension. numbers are borderline. 140/90 or so.to lose weight, plan on starting a walking routine. is it ok to do so with such numbers?

Hard to say: The numbers by themselves are not that worrisome. Whether or not you are healthy enough to do any sort of workout routine of any intensity is not something easily determined by your statement. Have you seen your doc within a year & been cleared for such activity ? Are you already very active & just adding this to your routine ?

Yes, but coordinate: Inactivity and weight gain may cause an increase in blood pressure, and exercise is typically beneficial. The recommendations are for at least moderate exercise (for walking, that translates to walking briskly), typically at least 30 minutes a day, 5 times a week. However, it is best to coordinate your plan with your doctor, as s/he will have you reassessed after an appropriate period of time.