Anyway, IIRC photography is generally not allowed, especially in the wards.
I feel that the hospital enviroment cannot be compared to that of streetshoots. A hospital is not strictly a public area. If you did take pics without the patient's consent, I feel you would be violating the patient's privacy. It would almost be like me going to your flat and sticking my lens into your bedroom and snapping away.
PS: My comments were in reference to the ward areas.
If you're talking about taking photos in the hospital proper, the wards etc, no they do not allow it, esp. if you're thinking of doing street photography style shots. At most if you want you can take a quick shot with a friend who's a patient, but that's about it.
They'll probably close an eye if you shoot outside and don't make a big fuss.