The first car that comes to mind that is fun to drive and fairly reliable is the Mazda Miata. Another convertible that is fairly reliable is the Buick Casada but it has a lot of buttons and is not as much fun to drive (don't get me wrong, it still drives well but it is not as sporty as the Miata).
A fun convertible that is not as reliable you can get the VW EOS.
There are not many convertibles in your price range. These three you probably can get used in your price range. I would suggest you test drive the first two I mentioned as at least they are reliable.
Best of luck.