I was able to install my Injen CAI w/o removing the front bumper except I have an aftermarket bumper...not sure if that helps. But yes it is possible, i've read from a post here somewhere of someone being able to accomplish that.
I didn't think it was possible, especially with the replacing of the wash fluid bottle. I've read someone doing it w/o removing the bumper though. Taking off the front bumper wasn't hard at all anyway...took me like 10 minutes my first time.