Similar to the Events and Reservations flow, you may support as many languages as you would like: just create a new template in that language from the rule editor. You can support up to 29 languages in total.
The language of the review will be determined on the basis of the language used in the conversation with your guests.
Reviews comes pre-loaded with 2 rules with templates in English and French. If you have no reason to use the French template, you may delete it.