Private Property Towing

I'm in Los Angeles California.

This morning, I walked out to find my car was towed away. There is a small medical center half a block from my house that recently moved in. There are a number of spots along the alley that runs beside the establishment. There have been no signs posted indicating that there is no parking in this area for the month that the establishment has been there. I parked there yesterday due to a lack of on-street parking in my area (as I have done a few times in the past month, as a number of my neighbors have also been in the habit of doing as well.)

This morning, they apparently decided to do some construction and began at about 6:30 AM with JACKHAMMERS and other heavy (loud) equipment that woke me up (in my bed, inside my apartment).

Apparently, this construction included the posting of a no-parking sign. On the sign is a phone number and ordinance number for the LAPD, but the number is invalid. Nowhere is the number of the towing company. I had to go inside the establishment to find out where my car had been towed. They indicated that the sign had been posted yesterday (I didn't see it when I parked, but, to be fair, it was about 30 feet away from my car and I wasn't looking around for a sign since there had been nothing previously posted) and that they had been putting angry notes on cars in the spaces for days (I have not gotten any of these notices on my vehicle) the secretary inside handed me a xeroxed page with the number and directions to the towing company's lot. There I got my car back for $210.

Where might I find information about signage laws, procedures to get my $210 back (civil suit?) as well as procedures for filing a complaint about the early morning construction right next to a residential area?
Anyone have any thoughts?

Thanks, in advance for any guidance!

-Doug