I've read that it's really important to keep your computer away from the mess (ours is). I just spent the entire weekend "cleaning" everything that I've ignored for the past 2 1/2 months (our demo was May 10th). We have a similar situation as yours-our kitchen/dining area (where walls came down) is open to the living room and our foyer is open to our daylight basement, so it was hard to keep things contained. They did have things closed off initially, but that went away I think when the dry wall guys were there, as there was work to be done on the foyer side as well (we moved a doorway). So I covered all the stuff in the adjacent living room (where we had moved a lot of furniture and boxes) with sheets etc. and also I covered our piano really well. I don't think the dust has hurt anything but who knows as we are still. not. done!

Find some washable throw rugs and junk rugs and pave the path from the construction zone to the bathroom, the halls, etc.

Hide your good electronic sound systems and get a cheapo unit you won't mind wrecking.

Get a flashlight and put it on the path to the breaker box so you can diagnose power outages. Study the breaker box while you still have light and comfort so you can negotiate it when you don't.

At Home Depot I got a "contractor pack" of plastic drop cloths. They are inexpensive and lightweight. I used it for the beds (pulled off nightly), my desk and computer, the food prep area and the washer and dryer. Plus I covered the chandelier because I don't like to dust that either.

The only place I missed was covering the bikes in the garage - the GC did a lot of sawing in there.

Every afternoon when they left I put down the cheap throw rugs for the family to walk on overnight.

All valuables hidden and locked up if possible. All precious breakables packed securely and moved to the opposite end of the house; as far away from the mess as possible. All everyday items in plastic bins within easy access. During drywall repair, and priming (fumes), a sheet covers the hallway opening to prevent some of the 'flow thru' although not entirely. Our one water supply is in the back of the house and the work is in the front so frequent trips to the water closet tracks dirt, dust and crud thru the whole house. Daily vaccuuming is a must for sanity. Be aware that drywall dust will find any available opening to float thru. If possible, opening windows helps. With the heat this summer, it's been few and far between that we were able to have them open. The few times we did, the screens were coated in drywall powder that turned to mud upon blasting them with the garden hose. I'm pretty sure 'construction muck' has become a food group for us! Ha Ha! Sometimes, the only sanity-saver is going out - to eat, to window shop, to wander aimlessly thru the grocery store all the while thinking about how much money I'm saving not buying half the ingredients since we're oven-less and burner-less anyway! We also use plastic to cover the big items that could not be moved to the other end of the area. The heavier plastic & tarps are re-used daily and the thinner plastic gets pitched once torn.

We have the same open foyer as you describe, and as long as we kept plastic on the kitchen/demo entrances we didn't see too much dust upstairs (our construction was 3 months). It's true that drywall dust had a way of getting through a bit anyhow, but that was only a couple of the days. The little throw rugs helped us a lot too, as others have mentioned.

In addition, if you'll have any wood floors sanded, that process requires extra protection. For our main floor refinishing we actually made a whole plastic tent over the foyer to prevent that fine dust from getting upstairs. We used so much plastic and duct tape for that adventure that we should've bought our own Ace Hardware franchise!

Love the advice! We're getting ready for one in 2 weeks.
A pathway to the bathroom also comes to mind. I would think that might need to be used every now and then?
And good advice about putting away the valuables. Noted!