77 is defo capris & T shirt weather for me, and I'm 'cold blooded'. The thing about October weather in So Cal is that when it's 77 it can be quite warm feeling in direct sunshine, but feel chilly if you're standing in the shade.
Dress in layers and get a locker. In weather like that I usually stow a hoody or jacket in a locker and start the day with a long sleeve T with a short sleeve T layered over & capris. You could also stow a pair of long pants. Shed the long sleeve T when it warms up then put it back on with a jacket in the evening when it cools down. Change into long pants if you feel like it. I wear capris and flip flops (hate shoes) in weather like this so if you see someone walking around in the cool/cold evening and night wearing capris, knee sox with toes, and flips, that's me! Function over form anyday!