1. When am I allowed to leave the hospital?
我什么时候能出院?
还能这样说：
When can I be discharged?
How soon can I be released from the hospital?
应用解析：
allow for sb./sth. 在计算、估计、考虑时包括某人或某事物;
allow of sth. 容许某事物;对某事物留有余地;
allow of no excuse 不容辩解
2. It's hard to say. It depends on your recovery.
很难说，这得看你的恢复情况了。
还能这样说：
It's difficult to say. If you have a good recovery, you can leave the hospital.
You can be released from the hospital after recovery.
应用解析：
You may depend upon it.
肯定无疑，放心好了。
3. Can you tell me why I can't be discharged now?
你能告知我现在为什么不能出院吗?
还能这样说：
Will you please tell me the reason why I can't be released from the hospital?
Could you tell me the reason why I can't leave the hospital?
应用解析：
discharge a gun 开炮;
discharge one's pistol in the air 假打，佯击;
discharge sb. from an obligation 免除某人的义务;
bad conduct discharge 撤销军职
4. You are going to be discharged tomorrow.
您明天就可以出院了。
还能这样说：
You are allowed to be discharged from hospital tomorrow.
You will be discharged from hospital tomorrow.