I know of at least 3 open groups which practice regularly. The format is usually touch hands, but if your partners agrees, I suppose they may accommodate your particular training wishes.
on alternating Thursday or Friday night @ Sifu Ma Kei Fai's school
hosted by
Roger Lam
Usually there are some senior TST students as well as a cross section of other branches and styles, and sometimes even boxing & muay thai
Every Friday night 9pm @ the park near MTR Tai Wo Hau station, there's a group of mainly WSL people. Not sure if they are still active.
I don't have the contact information. If you are interested, just show up and see.
on Sundays 10am-12 @ HK Polytechnic University
hosted by
a Yip Chun student
I haven't tried this group personally, so let us know what it's like.