I'll give you a little bump here, But I am not sure of where the Plaza resort is on St. Pete Beach. We usually go over there for a beach day on each trip to WDW and I spent a week at the Don Cesar last summer and I have never noticed it, and from the lack of replys to your post others have not either. As for being close to the airport, St Pete beach is not that close to the airport, unless you are asking about the City of St. Petersburg municipal airport, then it's in the city of St. Petersburg.
I use Mapquest to determine how close things are to each other, it will map out the directions and give you a detailed map with mileage. Good luck!