Our sages say that we didn’t change our language, clothes, and names and in that merit we were redeemed. However didn’t we have to communicate with the Egyptians in their language?
Indeed, the Maor VaShemesh in remazei Pesach writes that all Jews spoke Egyptian and what our sages meant when they said that the Jewish people were redeemed in merit of the fact that they didn’t change their Jewish names, language, and garb, it doesn’t necessarily mean they spoke Hebrew but that they spoke in a pure and refined language in Egyptian! Thats what it means to speak “Jewish”.
However the Maharsha says that our Yiddish in Egypt was Aramaic being that our Matriarchs were daughters of Lavan the Arami (Aramaic) and that’s why our sages say that the Targum or translation to the Torah was given at Sinai together with the Torah. Otherwise why would they need it if they spoke Hebrew?
The writing does not exclude speaking multiple languages; such that you would speak Hebrew to a Jew and Egyptian to an Egyptian.
A textual analysis of proper nouns suggests that cradle speech was Hebrew as there is no back-contamination of the proper nouns from Egyptian. Weight this as you will; it could have been unwound by someone who was smart enough to realize how this works.