CPSLO is probably about as selective as the middle-selectivity UCs, while the other more selective CSUs (SDSU, CPP, SJSU) are probably about as selective overall as UCR or UCM, but there can be significant variation in selectivity by major. The CSUs are also non-holistic in admission, using just a formula of GPA and SAT or ACT score (plus a few other criteria for CPSLO).
Most CSU students are in pre-professional majors, while most UC students are in liberal arts majors.