Coming to LA from NYC without a car. Am I screwed, or what?

Greetings. I'll be in LA for three months for work. How bad is the public transit? I assumed this has been asked before, almost certainly many times, so I walked through the FAQ of this subreddit and found it somewhat lacking.

I'm staying in Santa Monica, heading to Westwood for work most days, and occasional trips to pasadena.

I get that this is going to be a challenge, but is it going to be impossible?

Thanks.