You should be able to see it. When using a browser, you can see it to the right of the booking request/enquiry/message thread, in the 'reservation details'. If you can't see that, click on the red 'details' button and it should appear.
Under the dates/price etc that appears at the top, you will see a section About (name of guest) and the overall rating and number of stays. Click on the latter, and you will see the breakdown of ratings for cleanliness, communication and following house rules. It doesn't show you what score each host left, and it tends to round up scores to the nearest 0.5, so a guest who has 4.6* will show as having 5.0*, but at least it gives you some indication.
Likewise, on the app, you just need to go to the message thread with the guest and click on the 'details' button, then click on the overall rating, to go to the individual category ratings.