I'd say the HOA and the towing company.
California Vehicle Code §22658 was changed sometime in 2007 so that HOAs may tow vehicles for parking violations only if:
1) appropriate signage has been posted;
2) the vehicle has been issued a notice of parking violation and 96 hours have elapsed since the issuance of that notice; or
3) the vehicle is inoperable and the local traffic enforcement agency has been notified at least 24 hours prior to towing; or
4) the property upon which the vehicle is parked is improved with a single-family dwelling.
Since it appears none of the foregoing instances apply to your situation, you can sue the HOA. The property management company is merely an agent for the HOA and would not have independent liability to you.
In addition, since you weren't parked in a fire zone or blocking ingress/egress, I believe the towing company can also be held jointly liable. Under California Vehicle Code §22658(l)(1)(A), each time a vehicle is towed, the HOA is suppose to provide a specific signed authorization to the towing company and a representative of the HOA must be present when the vehicle is towed. I doubt that ever happened.
The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author (who is only admitted to practice law in the State of California). For specific advice about your particular situation, consult your own attorney.