I know they’re calling it #101slowjam where a section of the 101 on the east side is closed for the demo of the 6th street bridge. However, last I took the 110 around DTLA, which is their intended detour route, things were at a standstill crawl and it wasn’t even a peak drive time.
My suggestion is if you need to be downtown this weekend during the 40 hour closure you use metro trains and buses as its going to be a hellish drive. If the intent is catch the 5 or 60 from there find a better spot to grab it and avoid the congestion downtown. This is going to be a long 40 hour closure.