The best time to visit Los Angeles is rightly considered to be autumn when the West Coast of the United States enjoys the best weather: no winter rains and no summer smog.
From September to November, the air is not as hot as in summer, it's much easier to breathe, and the number of tourists is significantly less than during the summer months. The average air temperature ranges from +17 to +23 °C, which makes walking and sightseeing quite comfortable. The best time to swim in the sea in LA is September when the water temperature is about 20 °C. But do not forget that in the middle of autumn the night temperature drops to 12 °C. So take some warm clothes.