i'm actually making the opposite move in a few weeks, going from westwood to LB.

from the westside you can obviously ride up and down PCH or go over to the valley. i don't go as far as commerce but to get to DTLA/USC area there are many large/busy streets you can take though it's not so pleasant. Wilshire, Santa Monica, Olympic, Pico, Venice, Washington, Jefferson all go west-east til at least close to DT. streets south of Washington also go west-east but they'll take you through parts of south central. all of these can get pretty bad during commute hours and have more than the occasional pothole.