Fall is much better than Spring for azalea and rhododendrons. But everyone loves to buy things in bloom in Spring. It is however, starting to get a bit late. I am in NW Missouri and try not to plant after ~ October 15. I have planted as late as November 10th. BUT .... plants need to have time for their roots to get settled before they shut down for winter. If not, the plant has a higher probability of perishing.
It would be helpful to know the original poster's city and zone.
