Question
We have a steep hillside that we no longer want to weed wack every time we mow.  It abuts our neighbor's property, so we have to be careful with what we do.  I'd like to permanently kill the grass, then in the spring I want to plant ground cover (juniper) on the lower half, and flowering plants on the upper half.  Whatever I use I need to make sure it doesn't kill my neighbor's lawn or the adjoining lawn above it in our yard.  Can you suggest anything?

Answer
Round-Up 'drift' is not unusual when this chemical is used in orchards and other open spaces.  Stay away from it.  And it's not good for your local Birds and Bees, anyway.

Mow, then cover your Grass-and-Weeds plot with black Hefty bags secured with stones.  The lack of sunlight will kill the Weeds that are growing plus the Grass under there as well.  Till, water, then wait for more Weeds to germinate -- and a week later, cover again with more Hefty.  I would recommend Solarizing, but it has been a cool Summer, too cool for that.

Your Juniper and Flowers design sounds very nice.  And the whole plan is very sensible.  No one likes to mow on an incline.  Ground covers are the way to go here.  If you really want to enrich your soil, incorporate some Compost or Humus into the plot.  Tricky, but nothing compared with Mowing a Lawn on a 45 degree angle incline.