Can you give me an estimate of the number of people who speak English
as a first or second language in China?

Thanks

First language English speaker in China? I'm afraid none. Since even
in Hong Kong, few people would use English as first language (the
language you speak at home). As for 2nd language speaker, they are
plenty. Just try counting college graduates.

Thanks for the comment. 

I had thought about counting the number of graduates but this would
not give a very accurate answer.  In India where English is used much
more widely only around 80% of graduates speak it.  I had hoped that
there might be some Chinese census results which would contain such
details but I have been unable to find any.