For my last feature, I needed both an exterior dialog scene and an interior hospital room scene. I asked the local hospital, who basically told me to go take a hike. I think they were probably concerned about client privacy issues, etc.
So, for the exterior, I set up the camera on the street in front of the hospital, placed the actors on the sidewalk across the street and shot with a telephoto lens toward the building (to make it appear closer) with the EMERGENCY entrance sign in the background. They weren't too happy about it, but - as we were not on hospital property - they couldn't stop us (we had permission from the city to shoot on the streets).
For the interior, I arranged with a local college to use the training lab of their nursing department. It had hospital beds, gowns, IV racks, machines that go "ping"...everything we needed.
As far as the waiting room, I should think any waiting room would do. A little set dressing goes a long way.
You might have better luck getting the real McCoy; but, if not, the above worked for me.