Good question. Large majority of folks will be commuting via car during clerkship year. Assuming that you live in West LA near campus, the sites that are reasonable to consider bike, public transit, or Uber imo are Santa Monica, Reagan, and the VA. Cedars is iffy. I wouldn't for Kaiser Sunset. Not very reasonable for Olive View and Harbor. Keep in mind that public transit isn't always the most reliable, and you might want to consider something reliable during clerkships when you have patients waiting to be seen and residents/attendings waiting to round with you.
In terms of time spent on commute, it's largely dependent on that day's traffic situation. Olive View is sorta nice cause you're driving against traffic both ways so it's 35-40min ish. Harbor coming back in the afternoon/evening is slightly horrific imo. Even at your "closer" sites in Santa Monica and Cedars, bad luck with traffic in the evening can easily make your commute up to 30-45min (most of the time more like 20ish minutes).
I will say that if minimizing commute is something you want to do, you have an opportunity to prioritize that when you're ranking sites in our clerkship lottery during before MS2 year. I know multiple classmates that only did rotations in Santa Monica, Reagan, and the VA. The large majority of us will be scattered throughout LA however.