Did the Jewish inhabitants of Safed and Jerusalem (contemporaries of Rav Yosef Karo and the Ari) speak Hebrew when they learned Torah or did they speak Arabic, Ladino or some other language?
I saw a reference (quoting Rav Ovadiah Yosef) which claimed that they spoke Hebrew and therefore their seforim flow better than seforim authored by Yiddish speakers who mentally had to translate their Yiddish into Hebrew.
As I write in my upcoming book Lashon HaKodesh: History, Holiness, and Hebrew:
His slightly younger colleague, Rabbi Yitzchak Luria (1534–1572), also known as Arizal, is said to have been careful to exclusively speak Lashon HaKodesh on the Sabbath, and only use foreign languages as needed to clarify elaborate Torah-related complexities.
Source: Pri Eitz Chaim, Sha’ar HaShabbos (end of Ch. 21). A later account of Arizal’s behavior mentions that he was particular not to speak to anyone—even his wife—in a language other than Lashon HaKodesh. See S. Ashkenazi, Doros B’Yisrael (Tel Aviv: Don Publishing House, 1975) pg. 165.
From a passage written by Rabbi Hayyim Vital's son, Shmuel, and posted in an answer to another question here on Mi Yodea--
https://judaism.stackexchange.com/a/73292/1807
--it seems like the language spoken was Spanish: the passage mentions the term "El Diablo" as something one might say in la'az, the spoken vernacular.
(Although Rabbi Shmuel lived in Damascus, not Safed, presumably he would have spoken the same language as his father, Rabbi Hayyim. Rabbi Hayyim was the close disciple of Rabbi Isaac Luria, the Ari.)
The Ari was born in Jerusalem and lived in Cairo. He may have spoken a little Ladino, but most likely his primary vernacular was Arabic.
Aramaic was not spoken since the time of Amoraimthat is not true.