Will walking through the radiation oncology department expose me to dangerous levels of radiation?

No. The rooms where the radiation accelerator is located is shielded and have thick concrete walls. The hallways and rooms where people walk or work will have no radiation exposure.
Absolutely not. The radiation department is one of the most shielded and therefore well protected aces in the entire hospital for patients as well as other degrees f safety checks and protective guidelines.
No. Areas with possible exposure should be clearly marked according to well established safety regulations. The staff at any radiation oncology department will be able to guide you in terms of areas where one is not allowed. But generally most areas within a department are quite safe.
No. There is plenty of shielding to protect you and the healthcare workers. There are rules, and regulations to monitor these levels in common areas.