the public transportation is very convenient in that big city,so there(shouldn't )be any difficulty in traveling around
-不用“wouldn’t”

——betty said she would definitely be here before seven。 she’s never late
——but it’s half past seven now.she (can't)
be coming

不用“shouldn’t”

look at the dark clouds！there （should）be a heavy rain in no time
不用“would”

i tried to get through to her，but she simply （would）not turn on her cell phone as she was busy
不用“should”

这几个有什么区别.我希望有详细解析，谢谢

the public transportation is very convenient in that big city,so there(shouldn't )be any difficulty in traveling around
-不用“wouldn’t”
因为should为“应该”的意思，shouldn't为不应该。而would表示过去习惯性的动作或状态，因此不能用。
——betty said she would definitely be here before seven。 she’s never late
——but it’s half past seven now.she (can't)
be coming

不用“shouldn’t
can的意思有：1.客观的能力 2.可能性 3.主观上能够 4.推测
在此处为推测语气，表示“不可能”。而shouldn't表示不应该，自然不用。
look at the dark clouds！there （should）be a heavy rain in no time
不用“would”
should除表示"应该“外，还表示一种推测语气，此处为说话人的推测，would在上已提，它没有推测性用法。
i tried to get through to her，but she simply （would）not turn on her cell phone as she was busy
不用“should”
此句时态为过去时，would在此处表示过去的动作，should无此用法。
此处的解释不全面，如果不懂，请参考一下语法书吧！