I don't fax. Never have, never will. And, I was told, at the Polynesian, that they don't look at the faxes anymore. Haven't for a few years now. Why? Because so many guests were sending in faxes, the room assigners were getting bogged down by having to read 'em all.
Just have any and all requests on your original reservation. No need to fax. Of course, there are going to be those that tell you that they fax every single trip and have gotten exactly what they have asked for, every time. I maintain that they would have gotten what they asked for in any case. I would be severely put out if I put in my requests when I made my reservation, but lost out on my requests because someone faxed in their requests 3 days before arrival....and we had similar requests.