The Guardian has a regular blog section, in which anonymous aid workers go to church to confess their sins. That latest is entitled, "I only know 10 words of the local language". After reading, I have the feeling that the author was told in her younger years that she doesn't have "natural abilities" to learn languages. Or, the author really does hate learning languages.
What really bothers me about this confession is the monolingual perspective and concept of language pushed. It assumes that all communities, and the community she has lived in for 16 months, is monolingual. "As I write this, I’ve been in the same community for sixteen months and I can still only speak ten words of the local language." She doesn't give away what community or country in which she is currently living and working.
We need to stop speaking of "local language" in development. We need to start speaking of languages. The plural is important, so is the dropping of the "local". The prefix "local" is a poor assumption with a tinge of neo-colonialism. The assumptions overflow. It is based on an outsiders' view of communities. That our observation of language use is holistic, robust, and informed. That language is contained and bounded. Most important, it assumes and defines languages and languages use on behalf of its speakers and users.
Multilingualism is a reality in many communities. Globalisation has broken the "local". For example, many written forms of languages, particularly African languages and their orthography, cannot be seen without their colonial tags. Many of the non-indigenous scripts were not created locally, but by colonial administrators, anthropologists, and European linguists using Roman or adapted Roman scripts.
The two communities in northern Ghana I worked with for my PhD research were predominantly Dagomba. The "local" language could be identified as Dagbanli. However, there are other languages present. Qu'ranic Arabic is taught to children in a non-formal education program. English is the official language of Ghana, and the language of education from grade four onwards. Some communities member are not Dagomba, but have married into the community and speak a different "local" language. Fulbe semi-nomadic families can be found on the edges of many communities in northern Ghana, many of whom have migrated from Burkina Faso and speak Fulfulde, Hausa, and other languages.
There is no "local language", only languages.