Good Chance of Getting a D Senior Year; can I still get admitted into a low ranking university (CSUN)?

It is practically impossible to get an "F" in any California public high school, if you can write your name, and show up for cl and turn in your work. That is unfortunate, because it pollutes the gpa as a means of selecting applicants. That being said, I doubt that it will create a problem for you in being accepted to most California State University', including CSUN. Go ahead and apply, and prepare to be indoctrinated with the philosophy of mediocrity.