There is practically no reliable info on the bitcoin economy, in particular on the flow and ownership of bitcoin by country. (This is a serious problem for would-be investors.)

We can only note that more than 67% of all new bitcoins are mined by Chinese pools, which probably comprise mostly Chinese miners; and that bitcoin has practically no use inside China, except as an instrument of speculative trading inside the exchanges.  Until last October, variations of trading volume at those exchanges did not seem to be reflected in the USD transaction volume, which may mean that there was little deposit and withdrawal at those exchanges. 

There is efficient arbitrage between the Chinese and non-Chinese exchanges. If Chinese miners sold their coins only in Chinese exchanges, that would tend to depress the price there.  Then the arbitragers would immediately move those excess coins to non-Chinese exchanges, until the prices got equalized.

So, I would guess that it does not matter where the Chinese miners sell: the net effect is that a large fraction (if not most) of the bitcoins mined in China are eventually bought and hoarded by non-Chinese investors.