The bearings wouldn't be sealed and the axles wouldn't be retained properly, so I wouldn't trust it very far (or through water or dust), but I'd expect once or twice around the block to be alright. I don't think the axles could slide out of the hubs enough to get loose, though I'd want to check that before going for it. Given that you already know the axle is junk, though, I'd be inclined to just replace it and get it over with.