how big is greek life here?

Greek life is a huge part of student life on campus & especially if you want to party at all during the school year you need to be in Greek life

About 15% of SDSU students participate in Greek Life, so about 4500 people, according to google. There are other ways of building a community on campus because of how large the student population is, so yes there are attractive GDI's. However Greek Life is a great way to build social connections and a community, and it provides many opportunities that you might not run into if you weren't Greek.

Social life for freshman males is fairly miserable if they are not in a fraternity. It may improve in later years, but not by much. The number of 15% out of a student body is deceiving. All campus parties are held at the fraternities. All women are welcome to these parties, but no men who are not members of the fraternity are admitted. There maybe 40k students at SDSU, but half of them are commuters so they are gone in the evening and weekends. You can try to date, but upper class women won't date freshman. There are no clubs or hangouts anyplace close to campus and the student services provides no hangout opportunities during weekends. There is virtually nothing to do or places to go within walking distance of the campus. Some people will drink in their dorm rooms which are about the size of a small closet with a few friends, but that gets old pretty quick. Everything gets better with time and as individuals become more established on campus. However, underclassmen who are not part of greek life are socially screwed at SDSU.