If you're asking within the bounds of normal conversational I suppose "watashi no nihongo wa wakaru koto ga dekimasuka?" (Can my Japanese be understood?) comes the closest, but even so you rarely hear it phrased so directly. It's not the speakers fault, though, more that the Japanese are just odd in this respect to begin with. And you are hundreds of times more likely to be deluged with compliments on how good your Japanese is in the beginning when it really isn't than if you became serious about being good -- so try not to take those to heart either.