There are many similarities between our different religious institutions. Something that stood out is that English was fairly common in both signs and communication within the institutions, presumably as the most universally understandable option. Communication aiming to instruct or inform was especially likely to be in English.
However a recurring theme was that use of other languages was an important way to maintain culture. Often English was not used at all in religious services, suggesting this is imbued with more cultural importance. As Spolsky points out, “divine communication” tends to be a separate phenomenon to regular communication, sometimes requiring a different language. Jewish institutions tended to use Hebrew and the Saiva Manram tended to use Sanskrit in religious services rather than the first or native language of the visitors. These languages tend to be inherent to their respective religions. In contrast, Christian churches tended to focus on the language of the national heritage of their visitors, as Christianity has a weaker language association.
However, outside of religious services, most signage, socialising and communication tended to be multilingual and include code-switching or at least jargon-type borrowings. Arabic, Greek and Hindi were used in more than one institution. While a more comprehensive survey would be required, perhaps this indicates a large religious demographic in the corresponding cultures in Sydney.