If you’re driving, get the Sigalert app for traffic. Layers, yes. Walking on beach very much an option. Third Street in Santa Monica (and the pier, eh) very popular. My relatives from the Midwest love driving around Pacific Palisades, Beverly Hills, etc just to look at houses. Bring flipflops in case weather is good. I could’ve worn them today.
ETA: If it’s raining and you’re driving, be careful! Southern Californians do not drive well in the rain.