I have just used the script and it has worked flawlessly. Thanks!
So far I have only a small problem. I want to set es_ES.UTF8 locale. I have set it in locale.conf, locale.gen and I have called locale-gen. Now if I start arch using "enter-chroot", everything works as it should. I get spanish language in the shell, and when I call startxfce4 from the arch shell, programs are also in spanish. But if I start arch using "startxfce4" from crosh, or even with "enter-chroot startxfce4", LANG variable is not set, and everything is in english. Why is this happening? Maybe a bug in crouton scripts?