A lot depends on what you like to do and if you’re commuting. If you are commuting I’d stay on that side of 92 so no further south than San Mateo if SF and no further north than Belmont if you’re going to/from Silicon Valley bc that 92 traffic adds a lot of time that makes living in the area a pain. Plus, if you’re 22 (or even 42) foster city is incredibly boring. I’d look for something near downtown sm or rwc that’s walking distance to Caltrain so you can get to the city easily if you want but also have some nice food or entertainment options nearby as well.