Geeze that is a long list. I have busitis in my right knee. Actually the bursa (sp?) pad is ruptured. Gets all puffy when I bang on it, but otherwise no problems. The Meniscus tear is more of a concern. My guess is, if you can live with it, you can ride out the season. If it's really bothering you, go under the knife. The recovery time for the meniscus is relatively short, but there isn't a lot of season left either.
You're probably not going to do anything worse to it by going out and riding. Again, it's a comfort thing...
So much for the marathon eh?