我们换个话题吧！

Let's change the subject.

Let's talk about something else.

Let's talk about something different.

I'd rather talk about something else. (能不能换个别的话题。)

例句：

Okay, okay, I'll pay you back next week... (好吧，好吧，下星期我还你钱……)

Let's change the subject. (那，我们换个话题吧。)

言归正传。

Let's get back to the subject.

Let's get back to the point.

Let's get back on track.

例句：

Let's get back to the subject. (言归正传。)

Yes, let's. (对。)