The Westside is the part of Los Angeles that everyone visits and very few people walk. Most of it is reasonably walkable on paper — the blocks are normal-length, the sidewalks exist — but the shade economy is brutal. Palms are the dominant street tree and they throw nothing. The acacia plantings on the major boulevards are sparse and young. The result is that on any block where the buildings don’t pitch in, you are in the sun.
These picks all use buildings. The afternoon shadow off the Wilshire Boulevard high-rises in the so-called "Condo Canyon" between Westwood and Beverly Hills is the longest reliable shade on the Westside. The apartment blocks of Westwood east of the village throw narrower but useful shadows on the east–west cross streets. The Stay Cool model knows the difference between a 5-story Spanish-revival fourplex and a 30-story tower; the routing reflects it.
A note on the famous walks. The Venice canals are pretty but unshaded after 11. The Santa Monica Promenade is awnings on the east side only. Runyon Canyon is morning-only in summer and not really Westside. Stick to the corridors below in July afternoons.