Answer:
A context in which I would use informal English to communicate would be with my friends or my family group, that is, in a non-academic environment where the idiomatic expressions used to communicate are those of common speech, with a flat and non-specific language, and lacking of formalities or hierarchical structures within the syntax.
Thus, informal language avoids the use of unusual idioms, given the relative familiarity between the sender and receiver of the message.
