I agree with what Fr Peter has written, except perhaps for the following sentences which seem to not be completely correct, especially the second one:
But the Egyptians didn't speak Coptic, they spoke Greek.
.....But as far as I remember from the tables in Price's Acts of Constantinople, it was only in the 5th century that Syriac began to be used for literate purposes.
.....Everyone spoke Greek.
Maybe what is written concerning Syriac is true about Antioch, I don't know. But it is not true concerning Syriac generally. I just remembered St Ephrem the Syrian who did not even know Greek, Aphrahat, the Aramaic translation of the Holy Scriptures etc. Also, Syriac was a liturgical language long before the 5th century.
I also remembered the Coptic writings of the Nag Hammadi Library, the many versions of Coptic translations of the Holy Scriptures. So, not everyone spoke Greek. I think, it is more correct to say that the Greek influence was great in those countries that became hellenistic, especially in major cities.
Sorry, just my 2 cents.