Is it a good idea to do cardio and resistance training if you have lower bp?

How low? Low blood pressure can be defined in a relativistic way, such as comparing your blood pressure to a population of similar age & gender people. Or low blood pressure may be defined as a symptom complex including light-headedness, faintness, dim vision, general weakness. Symptomatic low BP is a contraindication to exercise until a cause for it has been determined.