Suggestions for copying iTunes songs and playlists to SDCARD/player and cleaning up the "name mess"?
I've not tested this on a huge hierarchy of nested folders, but assuming you use List view, giving you the opportunity to Opt/click the reveal arrow &amp; then select all -  

The Finder since Yosemite has a built-in Search &amp; Replace for file names.

Right click, Rename [n] items…



I just tested on some recipe text files I intentionally added accented letters to, but it ought to work on any file…



It does mean you'd have to go through each replacement, one at a time, á é í ó ú etc but it would get there in the end.

TextWrangler could do the same for the m3u file.