phranque - 4:50 am on Feb 23, 2012 (gmt 0)

there is no sitemap.xml markup to specify the language of the urls submitted or contents thereof.
that would be specified within the document itself and/or the HTTP Response headers.

note that the urls in the sitemap must be within the scope of the sitemap's location. (scheme, hostname, port and directory)
to submit sitemaps for another host you need to Cross Submit Sitemaps:
http://www.sitemaps.org/protocol.html#location

i mention this because i assume your english language urls are in a separate subdomain or subdirectory.