Turn off water at the main.
Closing the toilet lids and placing an object over your drains should help prevent evaporation and subsequent sewer gases. The oil suggestions are probably better options though.
If you are concerned about air conditioning inside the house, I might suggest you program your thermostat to come on at night to cool the house down to a reasonable level. Cooler temps outside means your AC isn't working as hard. Electric rates are typically lower at night than the day as well.
I would contact your local law enforcement agency and speak with their community services officer. You could request someone just check the property from the exterior every couple of days.