Go to www.hkrunners.com Down the left side there is 'HK Running Links' and a link to a list of clubs and organisations. There is a group I've seen along Bowen Rd, others meet at Happy Valley.
Have seen a group in the evening, probably midweek but can't be sure. It was a while ago as I moved to DB 2months ago but I'm sure there'd still be groups running in/near central. I'm sure I've read in some of the threads in 'Where to run' on the hkrunners website about who to contact/ where groups run. So that might be your best bet. Sorry I can't be more help!