Switching into CS will be very difficult. If you do not make the original threshold, then you will have an uphill battle to make the change later.
This is from the SJSU website:
Choose Your Major Carefully
It is important to understand that though all majors are impacted, the admission threshold for each major varies, depending on the capacity of the major to take new students, and the number of students applying for that major in that term.
We encourage you to apply for the major in which you intend to earn a degree. Change of major is prohibited during the application and admission process. After you are admitted, change of major is never guaranteed and is by petition only. Your mandatory orientation, advising and registration will all be based on your choice of major.
In addition, we encourage you to look at the admission thresholds by major at SJSU for recent terms, and to apply to an alternative campus that offers your major.
You must enter an alternative major on your application to SJSU. We will use this information for advising purposes only and will not consider your alternative major in the admission process.