Am using avamys nasal steroid spray once daily & nasal salt rinse. Can I salt wash twice a day? And how far apart from steroid use?

Yes. Salt water nasal sprays are helpful for patients with nasal allergies and sinus disease. The thought is that the saline rinse will help "was away" some of the inflammatory mediators and improve one's nasal symptoms. Nasal saline is also a mild decongestant.
Yes. Using a saline nasal wash should not be a problem--unless the solution has been home-made and is too hyper- or hypotonic.