Question: I came late to shul during the week and went to the ezras nashim to daven as no ladies come then. Was I included in the minyan?
Answer: The Shulchan Aruch (OC 55:13) writes that the ten men who make up the minyan need to all be present in the same room as the chazzan. The Mishna Berura (55:48) adds that it does not matter if they cannot all see each other providing that they are in the same room. The Shulchan Aruch (OC 55:14) writes that one who is outside a shul can join in through an open window.
Elsewhere, the Shulchan Aruch (OC 195:1) writes that a group of people who are split between two separate rooms can join together to recite the zimun if some of them can see each other through an open window. Nonetheless, the Mishna Berura (55:52; Shaar Hatziyun 55:53) questions whether davening in a minyan can be compared to zimun. He writes that while one can join a minyan from another room, it is best to go into the shul to daven.
The Aruch Hashulchan (OC 55:20) writes that as the ezras nashim is separated by a proper mechitza, any men davening there cannot join in as they are considered to be in a separate room, regardless as to whether they can see each other or not.
Thus, R’ Shmuel Wosner (Shevet Halevi 9:20:1) writes that while men learning there may respond amen, etc. as ladies would, they cannot be considered part of the minyan while there (See Halichos Shlomo, Tefilla 5:n18).
In conclusion, it is not ideal for men to daven in the ezras nashim as according to some poskim one would not be able to be part of the minyan while there.