What is the sign of the month of Adar I?

In the book Kedushat Levi (Parashat Shekalim, Tetzaveh), it was written: "The reason for Adar having sometimes 2 months, which is the leap month, is because it is known that the 12 months of the year correspond to the 12 tribes of Hashem.

 And behold, Adar, whose sign is Pisces, corresponds to Yosef, who is likened to fish, as it is stated (Genesis 48:16), "And let them multiply like fish within the land," for the evil eye has no dominion over him, like fish in the sea. Just as fish in the sea are covered, so the offspring of Yosef, "Ben Porat Yosef, Ben Porat alei ayin" (ibid. 49:22). And dag, rearranged, is gad, which is from the language of mazal (Shabbat 67b), meaning that in the month of Adar the mazal of Israel is elevated, and since Yosef fathered two tribes, Menasheh and Ephraim, there are sometimes two months of Adar".

 And see that the mazalot of all the months are called in the singular: Scorpio, Sagittarius, Capricorn, Aquarius, Aries, Taurus, Cancer, Leo, Virgo, and the new mazal of Adar is called in the plural: fish - which is a hint to the two months of Adar; for the second Adar has no mazal except that of the first Adar, and the mazalot of the months Tishrei and Sivan, which are also called in the plural: Libra, Gemini, are in truth singular terms, for Libra exists only in pairs, and likewise Gemini exists only in pairs, and it would not have been possible to call them in the singular, unlike fish, which could have been called in the singular, but it used the plural (in Hebrew) to hint to this.

However, in the commentary of the Chizkuni (Exodus 17:9), he wrote that there is no mazal at all for those born in the second month of Adar.

Likewise, the Baal Menaot HaLevi wrote in the name of the Rokeach and the Midrash that Moshe told Yehoshua in the war against Amalek, "Choose for us men" [Exodus 17:9] who were born in Adar II, because then they have no mazal and sorcery will not take effect upon them. And in the book Ya'arot Dvash (Part Two - Derush 8), he explained according to Kabbalah why, in truth, those born in Adar II have no mazal. And it is known that the month of Adar is a very favorable mazal for Jews.

Good luck - Menasheh Yisrael