Camry V6 used the same engine as Avalon. 2006 Avalon EPA is 20/28mpg local/hwy so your Camry should get about the same mpg. I got a 2001 Avalon EPA 21/29mpg local/hwy. The car is still getting that mpg(25mpg combined) now with 183K miles on it.
I would start with a tune up and fuel injection cleaning to see if mpg improves.