The best thing you can do is pool running. They sell a kit that is pretty inexpensive at sports authority or online that consists of a bouyancy belt, shoes and weights. This is supposed to be the best substitute for running and has zero impact. The eliptical helped me when I couldnt ride a bike for about a month because it mimics a pedal stroke, but the only thing it will help you with as far as running goes is to keep your aerobic endurance up but it uses different muscles.
Anyway good luck recovering I just had my meniscus cleaned up yesterday and hoping for a speedy recovery at least to the bike if nothing else.