No. You're going the wrong way. You want the Number 11. It stops in front of the post office.
不去。你乘错车了。你要乘11路。它在邮局门前停站。
I'll have to ring you back, as I need to have a look at my diary and I haven't got it with me.
我得(等会儿)再给你回电话,因为我要先看看我的日记,而我没有把它带在身边。