The apartment complex has their parking policy on file with the towing company - the towing company can tow at will - from what I have read this is legal.
The complex has a couple different types of parking spaces:
Unmarked parking spaces
Handicap parking (clearly marked)
Parking garage (which you have to have a remote for)
Future resident parking (located outside the complex entrance)
Other than that there aren't any spots that specifically state "Public" or "Visitor" parking.