Is a BP reading of 150/90 consistently enough to start medicine to lower it?

Yes. Per jnc-7 criteria, you are in stage 1 hypertension and need a medication to lower it. In addition to a medication, continue working on your diet/exercise routine.
Yes, if you can't. Chronic high BP is a major cause of heart attacks, strokes, renal diseases etc...Thus treating to goal less than 140/90 is recommended. 150/90 isn't terribly bad, but if you can't do it on your own with diet/exercise/wt loss etc...Then some mild med is not unreasonable. If you have diabetes, high cholesterol, or family strong history, then definitely yes... Stay well, gibby0517! good luck..