Traffic Lights, Signs and Controls: Traffic Signs on Private Property

My question involves a (potential) traffic ticket from the state of: California

If a local business puts up a sign saying "Right Turn Only" at the exit where their parking lot joins the roadway, am I legally required to obey it?

Same question for an "Exit Only" sign for a business parking lot. If a sheriff saw me pull into a private parking lot the "wrong way" and somehow knew the signs facing the parking lot existed, could I be ticketed?

Thanks

Traffic Lights, Signs and Controls: Traffic Signs on Private Property