Is it safe to have gallbladder surgery if you still have some past mono symptoms from prev infection?

Depends. On what symptoms you are having. Minor health issues would not likely be a concern, but weakened immune system with weight loss or low white blood cell may not be good for elective surgery. Please review in detail with your surgeon before any surgery is scheduled.
If your doctor . Says yes it is safe , once removed th source of infection will be removed.