I have successfully used regular copy paper for paper piecing Ethel. There are 2 tricks I use with it - first, I pre-fold all the lines before I sew on it. Second, if I have any trouble tearing it off, I spritz it with a little water, then it comes right off.
Also, before you have Kinko's make all the copies, have them make one so you can check to make sure that it copies to the correct size. I know that when I use my copier at work, I have to set it to copy at 101% so the copies are right.
I also use the thinner sandwich wrapper paper. Then, instead of photo-copying the pattern onto it, you can staple a bunch together (like 10 of them) at a time, then, stitch on all the lines of your pattern (without thread), using a long stitch length. So you would need to have 10 or so good copies to sew thru' to mark the others.
And I always make sure I have extra copies too - just in case! :wink: