Poor at

Perhaps:

'We Japanese are poor at foreign languages.'

'We English aren't very good at foreign languages.'

MrP

I think it's wrong to say like that.
I mean grammatically it doesn't sound really weird.
I am pretty sure that everybody will understand it if you pronounciate properly.

I saw many Japanese speaking English poorly, but when you are learning different languages it's always taking time. Besides, you should count individually, so it should not be "we".
So it's probably not

You can parse the noun phrase "we Japanese" as ("we"=a determiner of "Japanese").

'Good at' and 'poor at' languages/tennis/chess/playing the piano sound fine to me too, Taka.

OK, now it seems like the use of 'poor at" is not really wrong.

Here another problem is why 'poor at foreign language (singular without an article)' sounds weird whereas 'speak in foreign language' is fine.

Why?

Speak in foreign language does not sound fine to me. It also needs the article.

Google hits a couple of 'speak in foreign language' s.

FYI:

The spiritual gift involving ability to speak in foreign language(s) not previously studied or to respond to experience of the Holy Spirit by uttering sounds which those without the gift of interpretation could not understand.

The student is following the rule: use a noun after "poor at" (e.g., poor at golf, poor at playing the piano, and even poor at Language as a whole), but the noun phrase "foreign language" isn't an umbrella term. It represents more than one foreign language, so -s is required.

FYI:
The spiritual gift involving ability to speak in foreign language(s) not previously studied or to respond to experience of the Holy Spirit by uttering sounds which those without the gift of interpretation could not understand.

http://www.christcent