Gymboree HK has the Baby Sign Sing and Play classes. I went for the trial class, but was not impressed of the hygiene level. Their props are smelly! Now i play the Baby Einstein First Signs DVD for my gal occasionally. She signed mommy and daddy sometimes...dunno if it's fluke. Haha
You can also click on the Baby Signs? banner ad at the top of this page and see what they have. There are Parent Workshops and Sign, Say & Play? classes to choose from --all conducted by certified Baby Signs? instructors.