This is also another method to use, although with streaming music more data is used. I think you can download the music to your phone from Google Music. There is a plug-in (Google Play Music Manager) that installs on your Mac that will upload all your music to Google Play Music. It takes a little time. Once it's done you can go to the Play Music web-site and create and arrange your playlists via Safari. It's a lot easier to do it that way than on the phone IMO.
I did set this up and was going to use it. I went as far as to upload all my music. I still keep it in sync too. For my purposes I just liked how iSyncr works. I upload specific playlists because my wife, daughter and I all share a single iTunes account. I really don't want Beiber fever on my phone's music player, lol. Although looking at it again for the purpose of this post, it looks like you can specify playlists for automatic upload.