I would say not enforceable, but if your car gets towed that would suck. Call 311 and ask.

Let me tell you a story that happened to me a few years ago. I parked on the street near my place of employment, same street I always parked on. When I left work, I was greeted with an empty street; every car on the street (including several of my coworkers’ cars) had been towed. Signs had been placed up and down the street reading “No Parking 5pm-10pm” (or something like that) On trying to fight the towing charge, we insisted that there was no way the signs were there when we parked our cars earlier that day, but the parking court people said that they had been there 72 hours prior (even though they weren’t the ones that had placed them, and really had no basis to make such a statement) Even though I could prove that at least one of the signs hadn’t been there: it was on a pylon that I would have had to drive over in order to park where I had parked.

The worst part? The excuse they gave getting the permit for clearing the street was “filming”, but instead it was being used for valet parking for a party up the street. Honest to god.

^^^^
That’s almost as lovely as last Sept. when hundreds of cars were towed (including mine, natch) on Sunset for a Sunday triathalon. There was ONE tiny sign on the whole block.
I later found out while researching the triathalon that it wasn’t for charity, nor was it primarily city-sponsered, but run by a private company for-profit. Hmmmm.