In HK on 28th Mar to 2nd Apr. Is evening temp cool enough to wear jacket or light clothes ok? Help!!

It is no need to wear jacket and I suggest you to take your summer clothes and a thin coat in case of the rainy days.

I came back from HK a couple weeks ago and it was already quite warm. You may need a light jacket for the evenings, but you will be most likely wearing shorts all the time (excepts you want to watch out for mosquitoes especially if you plan to go to the New Territories).