Hi! You’re in for a treat. Central Oregon in September is so beautiful.
I have several recommendations for you. Don’t miss the High Desert Museum, which presents natural and cultural history and also has live animals on site. For hiking, try Smith Rock State Park, the Deschutes River Trail, or the Cascade Lakes region. Tumalo Falls is near Bend and easy to access. The Newberry National Monument offers cool volcanic history and views as well as a waterfall, Paulina Falls.
Take a stroll through Sisters – a fun little town with Western flair. Many events take place in Sisters in September, too. There is a ton of great dining in the area – try the Old Mill District or downtown in Bend for starters.
What else do you want to know? Have a great time!