Yes, responses can be in any language.
Related Articles
How does an individual invited to my Digital Guestbook start their response?
Can an individual invited to my Guestbook change the Guestbook Prompts?
Does an individual invited to my Digital Guestbook need access to WiFi and a smartphone/computer?
Can people invited to my Digital Guestbook submit more than one response?
How do individuals invited to my Digital Guestbook know if their responses were successfully uploaded?