The 4-year and 6-year graduation rates are standard stats that you can readily look up, e.g. at the US Dept. of Education’s “College Navigator” website. For SDSU, the current 4-year rate is 34%, while the 6-year rate is 73%. For Redlands, the 4-year rate is 65%, while the 6-year rate is 74%.
Low 4-year graduation rates are typical throughout the CSU system. For the system as a whole, the 4-year graduation rate was recently reported as 21%. At San Marcos (the other CSU in San Diego County), the 4-year graduation rate is only 14%. SDSU’s 34% rate is probably one of the highest in the CSU system.
https://www.mercurynews.com/2017/06/07/1-in-5-csu-students-graduate-in-four-years/
Many CSU students are not traditional residential students; they are local commuters juggling school, work, and family, which can make it difficult to stay on track.
Redlands does have a much higher acceptance rate than SDSU (75% vs. 35%), but the difference in the enrolled student body is not that great, at least as measured by standardized test scores. For example, the 25%-75% SAT range for fall 2016 was 980-1190 at Redlands and 1000-1220 at SDSU. Most of the difference is in the Math SAT, which may reflect the fact that SDSU (but not Redlands) has large engineering and computer science programs.