In my experience it takes 2 or 3 hours to get enough confirmations for a single transaction to be considered accepted, depending on how many blocks are found at that time. So buying the BTC from China will be one transaction and sending it to an exchange address in the US will be another and the whole process should take about 4-6 hours. So far, in that timeframe, I haven't seen bitcoin's price move by more than a few hundred dollars.
I think 4-6 hours is way too long to be exposed to btc price risk. Say it I transfer $10k USD and if price drop $200 then equivalent to loss of 2%. This is not trivial loss in terms of international money transfer.