Here is some offical information about getting married in Hong Kong. You can get married in Hong Kong irrespective of nationality and you do not have to be resident in Hong Kong. You can apply by mail from outside Hong Kong.
Marriage registration (in Hong Kong)
Each English web page on this site is linked to both traditional and simplified Chinese versions of the same information - just click on the “fanti ban” or “jianti ban” tabs near the top of the page.
Has anyone got married there? It looks like a lot less hassle than doing it in Taiwan.