A signature isn't required for your delivery to be left, but it's ultimately up to your carrier's discretion whether it's safe to leave your box or not. If there's a specific location you'd like your boxes to be delivered to, you can add delivery instructions in your Account Settings under the Shipping Details section.
Our food is shipped in insulated boxes that should stay cold for several hours upon delivery. But, it's best to unpack and refrigerate your food as soon as possible.