be off to: 去……地方

Next year we'll be off to something else.明年，我们又会转向其他的东西。

set off for: 出发开始动身前往赛跑。

Leaders set off for Shanghai just after ten. 刚过十点，领导们就动身去上海了。

What time will we have to set off for railway station tomorrow?我们明天得什么时候出发去火车站?