Connecting to Android

I'm not a beginner in electronics but neither am I an expert programmer so I don't know the best way to connect an arduino to Android. I've looked into USB connection and also by bluetooth but the code seems complicated for both. Would one method be more advisable than the other?
I want to use sensors on the Arduino to record values and then display them on the Arduino screen.

Bluetooth is much easier to implement, and it's wireless.

aaCOJ:
I've looked into USB connection and also by bluetooth but the code seems complicated for both.

You clearly haven't been looking hard enough. Sending data to Android via bluetooth involves no more programming than sending it to the serial monitor, and involves about $4 for hardware.

You might find the following background notes useful

http://homepages.ihug.com.au/~npyner/Arduino/GUIDE_2BT.pdf
http://homepages.ihug.com.au/~npyner/Arduino/BT_2_WAY.ino