What to do when sinus infection comes back after surgery?

My sister in law has a hereditary sinus problem and she just recently had the surgery where they sc out all the gunk in her sinus cavities. During surgery they found little tumors that were starting to form. This was over a month ago and the infection is already back. Shes been on every antiobiotic known to man of course and the only thing the Dr. can tell her is to move to the coast where there is naturally salt water in the air. Funds prevent this from happening anytime soon. What can she do in the meantime? (natural remedies very welcome!)