Search with prompts that could include “what languages are spoken in…” or “demographics of…” and include your city, state, province, or metropolitan area. If you do live in a city where many immigrant communities are focused in special areas, searching, “diverse immigrant areas in …”. This might give you a starting point, if you don’t have one.
This is helpful if there’s an idea of who might be in the area, but there are no details otherwise available. For example, “Syrians in New York”, or “Nepalese in Chicago”. This should be searched in Google AND on Facebook. Many people are making public Facebook groups like this now, so that they can connect with each other. Finding a group in a specific city could give clues of the size of the community, some local connecting places, events, and perhaps a few key contacts. Using discretion as to how to reach out would be key.
Search “Moroccan Food”, “Ethiopian restaurant”, “Persian Cultural Center”, or just “Cultural Center”, or “Burmese Market”. If the goal is to learn about and reach out to other cultures in the community, one great way of starting to build relationships is to become regulars at these very restaurants, markets, cafés, shops, etc.
For the USA and Canada, PeopleGroups.info, a collaborative work under the International Mission Board (IMB) is a good place to start. https://www.peoplegroups.info/. This database relies on US and Canadian census data, specifically the studies called “5-Year US ACS Foreign Born and Language Spoken at Home” and the “Canada Census Language Most Often Spoken at Home and Foreign Born”.
In some countries you can access census data online at many different levels. As suggested it might not always paint the whole picture but it gives a good start. The reason for gathering such data is to enable the planning of national and local services and so data is often available at local government level either on public websites or by asking. Some websites make finding some of the information fairly easy, others can be bewildering to navigate.
You might be able to do a simple informal survey to find out the languages spoken by people in your church and other social networks. Ask someone who already trusts you, and then they can connect you to someone who trusts them. Building on existing social trust can take you far. Staff in schools, hospitals, doctors surgeries, local authorities might also be able to tell you some information including what languages they make materials available in or point you to non-confidential sources.
Beware however, that simply asking people in the street that you don’t know what language(s) they speak might not always get the answers you expect. Some may see it as suspicious, intrusive, or even racist. Some people have been made to feel ashamed of their heritage and so might not tell you if they speak a minority language and simply tell you only the most prestigious language they speak. They might also assume you don’t want that much detail or have always been told that their language is ‘just’ a dialect.
For deeper research and more thorough information gathering, you might decide to get more official data. In a number of countries you can make reasonable requests for data under freedom of information laws. GDS researcher, Peter, searched for sources to an online claim of 300 languages in London schools, and eventually, sent a freedom of information request to the department of education in hopes of getting some official records. He also says that in another case, “...a simple email to a school secretary told me the number of languages spoken at home by pupils in my old high school”.