Xmap is compatible with JoomFish and it can generate the sitemap for any language supported by JoomFish by adding the parameter '& lang=XX' at the end of the link to your sitemap. Eg:

This is the english sitemap:

index.php?option=com_xmap&view=xml&sitemap=15& lang=en

This is the spanish sitemap:

index.php?option=com_xmap&view=xml&sitemap=1& lang=es

NOTE: Remove the space between "&" and "lang" as it was added to avoid a problem with the editor