THE ORIGINAL ANSWER SHOWED THE VIEW FROM NEW ZEALAND. THIS UPDATE IS EXCLUSIVELY ABOUT THE VIEW FROM HONG KONG.
Here's the view from the southeast coast of China (roughly Hong Kong) at just before 6am:
You can see the lat/long coordinates at the bottom of the image.
Mars, Venus, Saturn, Mercury and Jupiter form a nice conjunction just before sunrise, but by then the sky will probably be too bright to be able to see Mercury very easily. Venus and Saturn, and possibly Jupiter, will be bright enough to see if you have a clear horizon. The green line is the horizon, so the Sun is just about to rise.
What constellation(s) are the 5 planets in during their conjunction?
Venus, Mars and Saturn are in Capricorn, while Jupiter and Mercury are in Aquarius.
How long will the conjunction last?
The planets actually move quite slowly through the sky (that's why they're called 'planets' - from the Greek word for wanderer), so this grouping will last for quite a while, and on 30th of March, the Moon will join them, although by that time, Mercury (and probably Jupiter) will be lost in the Sun's glare.
How far up in the sky does a person in Hong Kong have to look to see the conjunction, in laymen's terms?
Jupiter and Mercury will be just a couple of finger widths above the horizon. I don't know what the view is like from Hong Kong. If you're looking across the water, you might be able to make out Jupiter and Mercury. Venus will be easier to see; it will be about three fist widths above the horizon, at an angle of 30$^\mathrm{o}$. Mars and Saturn are both dimmer than Venus, but if you can see Venus, you should be able to make them out.
If you have any further questions, make a new post asking them.
I will also note, that astronomers wouldn't quite call this a 'conjunction'; see John Holtz's comment regarding this.