Get a desktop Android emulator like Youwave or Bluestacks. Then install and run Opera Mini for Android. Note Opera MINI - NOT Opera MOBILE. The "MINI" version for android compresses in much the same way that the java app does, so its a pretty good indication of how your site will perform on even a dumbfone with Opera Mini as well. But try Youwave first. I used to use Opera Mini on my Bluestacks quite regularly, but it always crashes now - not sure whether is Bluestacks or my PC with the problem, so maybe try Youwave.