Is it okay to use sprinklers every day in Perth?

No it isn't - in winter we don't get that much rain, but sprinklers should only be put on if there has not been rain for a long time (which is quite common!). However, it is best just to monitor lawn and plants to see what they need for water requirements. In summer there is a watering roster so you can only put sprinklers on a couple of times a week.