Hang Seng index, go or no go?

I'd look at the Greater China region as a whole. A single country allocation is very high risk and doesn't provide much diversification.

If you are buying and only looking to hold Hang Seng as say, 5% of your entire portfolio, then by all means.

Look at the chart of the index.

Never buy on a downtrend (e.g. catch a falling knife) as you never know how far the price can drop.

It would be helpful to look at the technical indicators (E.g. moving average). 50 MA, 150 MA and 200MA to determine if the price is on a downtrend or uptrend.