Yes, your quickest/cheapest option would be to connect your phone directly to the AUX in socket (using a male to male 3.5mm lead) then hit 'CD' again until AUX comes up on the display and your phone music/sound is passed through your car stereo.
I very recently got completely bugged by all the cables hanging around with this option and built an Airplay solution so that I could quickly pump music from Spotify/iTunes etc. 'wirelessly' into the stereo. As I'm an Apple user though, I've no idea if that could/would work from an Android phone.
I should add that, although I could have just used a Bluetooth adapter to perform a similar function, I don't have the Bluetooth module in my car and I find Bluetooth to be a ballache to connect/manage in cars I have used it in. Also, Bluetooth compresses the audio transmitted, essentially impacting the quality of the audio received by the stereo - that's fine for a phone call, but not so good if audio quality is your bag.