Any Cali/San Diego stuff to not miss while visiting???

K • ✨
I'm visiting San Diego in a few weeks, but will have my own car and I'm going with my fiancé and his brother to explore and just see the west coast
My fiance's other siblings live out there but have to work so we need some ideas of fun and affordable things to do! 
Any suggestions besides the beach of course would be appreciated immensely ☺️