Are there advantages to going to the CSUSB program if I'm already here for for my undergraduate?

There might be! You already know many of the professors in the graduate program. Whether you know it or not, many of your professors from your undergraduate classes also teach at the graduate level. The institutional knowledge, personal interaction and the routines of your department are already elements you know and are familiar with. Be sure to consider all options and talk with your advisors early to answer any questions you may have.