It seems Adelaide does not presently have a critical mass of active Tableau Community users for it to be worthwhile.
Why not create an Australia group? We can still keep all existing Australian city groups (e.g. Sydney, Melbourne, Brisbane, Perth, Adelaide, Canberra and any others). The largest cities have enough active users for some local discussions and events. But for the rest of us, a single Australia group might work better.
Feel free to cross-post this question to other Australian local user groups... the other advantage of an Australia group would be that discussions that are relevant to the nation-wide user community could live in that group, no cross-posting required!