I can't finish this.

我吃不完了。

I can't eat another bite.

我一口也吃不下了。

I really like dessert, but I can't eat it now, can I get it to go?

我非常想吃甜点，但是现在吃不下了，我能带走吗？

Do you have a doggie bag?

有打包带吗？

Do you have something I can put this into?

有没有什么东西可以把这个放进去？

Could you put the leftovers in something, so I can take them home.

你能找个东西把剩下的菜放进去吗？这样我可以带走。

Dialogue:

A: I can't eat all of this, can you wrap up what's left to go?

我吃不完了，你能把剩下的给我打包吗？

B: Certainly, I'll take care of that.

当然，我会帮你弄好的。