We're the same way, except we don't live in the country, we live a few minutes outside of NYC.
Any nice weather and my front door is usually not only unlocked but wide open so I get a nice breeze from the front door through the living room and kitchen to the back sliding glass door(also open). Sometimes I will lock the screen door, but usually not.
Today I took the kids out to run errands and when we got back the door was wide open. I was annoyed, not because the door was unlocked, but because I had the a/c on. That actually happends pretty often, my son is the main culprit. *I* always lock the door when we leave.
If the front door is closed, it's usually locked, but I'd say from April-October I have it open at least part of the day.
My back patio doors are almost always unlocked all spring and summer because we're all going in and to the deck or pool or backyard.
That's during the day, at night everything is locked up tight.
My garage door(the regular person sized one, not the big ones) is always closed, but I have a bad habit of leaving the key sitting in the lock.

I really try to remember to take that in at night though.
We do have a big dog who will bark her head off if anyone comes near and an alarm that is on every night.