iPhoto on IOS does not yet support ratings like iPhoto on your mac.
As a cumbersome work-around you could use the caption field to add rating numbers. And to transfer ratings to your mac create different albums or Shared Photo Streams - one album with 5* rated photos, one album with four star rated photos, etc.When you sync these albums to your computer via iTunes, you can assign iPhoto ratings on your mac to each of the albums afterwards.
To use Shared photostream (one for each rating) see here: iCloud: Using and troubleshooting Shared Photo Streams
Thank you very much for your expertise, but the work around is very Cumbersome indeed... Just frustrated that there isn't something easier. I don't have the time to work this as a work-around with all the photos I need to edit on a regular basis. And I don't even care about 1-5 stars... like/don't like, one or the other, yes/no... Not rocket science, just very, very basic mobile picture selection. I do 2,000 or so photos at a regular wedding and I can't stay in front of my main production machine all day picking things out, so I bought an iPad for very simple ghestalt editing on the road and for display purposes when I show portfolios to potential clients...