Susan,
I think your idea is grand! I have seen several people that have pieced or appliqued curtains for a sewing room, kitchen and even a living room area. They are fabulous. I say, go for it! It will be a fantastic experiment in design for you, and I bet it will inspire you on a daily basis to sew and quilt.
I vote if you are going to the Dear Jane, (I am a drop out of DJ - after 60 blocks) that you might want to enlarge the patterns just a little. They are pretty small blocks and if you are putting them on curtains...the lovely designs may be a bit small to see and admire. But try it...if you like.
You might just do some quick DJ's with just an iron on without taking the time to do a small zig-zag around the designs....If they are hanging up as curtains....And how many times will you really take them down and wash them? If you think you want to do this and finish the edges...then I vote for the machine zig-zag...because it will protect all your raw edges.
Note of caution: The DJ patterns that we are seeing, (not the originals)were first designed by a person that had never quilted. Thus in many of the patterns, there are litterally less than 1/8th inch seam allowances. And those may come out when washed repeatedly.
DJ is fun and to have a group meeting doing it together each month is a lot of fun, and there are several groups online that are really cool. I joined two when I was doing DJ and participated in several swaps. What a great group of quilting gals...and a world of experience and encouragement.
I encourage you to do the curtains and enjoy the experience.
If you get a little fabric that doesn't behave well after a washing or two, well...isn't that what fabric glue is for?
lol....
just Jan