The rangers were mentioned a few times in news reports. There is no doubt they existed at the time. One mention was when the car seat was handed in to them and the another when they helped search the beaches. However, to check if Rangers were employed at the time as paid lifeguards and answer other questions about what they knew about Julie Cutlers car etc, I rang the Cottesloe Council who employed them. The very friendly woman said she would be happy to find out the answers, but I needed to make a written request to access the records from 1988. However, when I did this I received a written reply that they were unable to access the records to answer any questions about this topic.
I'm thinking the rangers discussed would be council rangers as opposed to beach patrols. They usually didn't start until about Sept/Oct and finished up in around April. Council rangers came out as required.