Its not right on the Piazza Navona but the location is great...

http://www.hoteladriano.com/

I'm about to book but any last minute recommendations would be considered.
Thanks.

We stayed at an apartment in the ghetto area late February/early March. It is an interesting area and a short walk to the Pantheon/Campo de Fiori/Piazza Navona.
The Hotel Arenula is in this neighborhood and within your price range. It is recommended in Frommer's guide and has fairly good reviews on trip advisor

We're only in Rome overnight when we arrive and one night when we leave and my kids insist we stay near Piazza Navona. I got mixed reviews on Genie from Trip Advisor.