As I recall, 6 out of the 30 people in my group were from a Cal State. However, this may just mean that more UC students than Cal State students apply to USC School of Pharmacy. In addition, doing the answer and question session, 1 out of the 3 USC pharmacy students graduated from a Cal State.
I don't think graduating from a Cal State would dramatically affect your chance of getting accepted to USC. However, I do feel that Cal State graduates have to do a little better than UC graduates academically in order to get accepted.
USC accepts their students based on a point system: 25% overall GPA; 20% pre-reqs GPA; 20% interview; 10% essay; 10 % pharmacy related work experience, leadership, recommendation letters; 10% degree; 5% academically and professionally prepared for pharmacy school.
As you can see, more than 50% of the points have nothing to do with grades. You should concentrate on doing well in your classes and definately apply to USC; there is no reason why you shouldn't apply. Good Luck.