If (all) propositions intrinsically have a logical structure, then does an english speaker's utterance of "I will go to the store unless you already bought milk" typically express a proposition with the structure ~P>Q, or one with the structure PvQ?
Does it depend on the situation? Who bought milk last time? :)
It seems better to say that propositions expressed by natural language sentences only have a logical structures only relative to a choice of logic, and a method of translation.