A normal program if daily watering was a possibility would be to spray to kill the weeds and then overseed, plug or sod. This is not feasible with twice a week watering or any watering restrictions. You can core aerate and overseed while weather is still cool and get some seed to germinate in the aeration holes. This will provide a little more grass. Otherwise, mowing the weeds is likely your best course of action until water restrictions are lifted.
