Normally how long after open abdominal surgery for gallbladder removal before yoga and light cardio workouts can resume without causing more pain?

Consult your surgeon. I recommend that you consult your surgeon about the risk and befits of the surgery as well as what to expect for outcome and recovery. Wishing you the best.
6 weeks. Open abdominal surgery involves cutting through layers of muscle tissue. This can take 6 weeks to heal, sometimes more if patients are older or diabetic. I recommend avoiding abdominal crunches or other abdominal toning exercises for 6 weeks. You can usually restart mild aerobic exercise in 2-3 weeks. Remember, "no pain, no gain" does not apply after surgery. If it hurts, back off for a week.