Any advice on low GPA, high ACT?

The Cal states you mention all admit based on CSU Capped Weighted GPA and test scores which calculates out to an Eligibility index. A lower GPA can be compensated with a high ACT which your son has with an ACT of 33.

ACT 33 conversion to SAT is around 1470.

EI= (CSU GPA x800) + (SAT Math+EBRW)= (3.0x800)+(1470)= 3870.

For CS:
SDSU EI is around 4200+ so a Reach school.
SJSU EI was 4725 so again a Reach school.

For CPP, he might have a chance so I would definitely apply.
Sonoma State is a solid Match.

Other options would CSU Fullerton, East Bay and San Francisco State.

Except for CSU Long Beach, SDSU, Cal Poly SLO, SJSU and maybe CPP, he would have a good chance at the rest of the CSU’s.

Below is the CSU impacted matrix. Have him apply to 1 or 2 non-impacted CSU’s as safeties. SFSU is not impacted for CS.

https://www2.calstate.edu/attend/degrees-certificates-credentials/Pages/impacted-degrees.aspx

Best of luck to him.