Most definitely! Especially if you can place the speakers close together. With the speakers side-by-side, and you listening about 2' away, if you move your head back and forth to center and off-center on each side, you will find a "weird spot" where the sound suddenly sounds very odd. That is proof that the speakers are out-of-phase. It kinda sounds like the audio moves into the middle of your head! ;)
Another thing is to do an A/B test, with a song that has a strong bass track. With the speakers side-by-side, if one is out of phase, the bass will be almost non-existent, or very weak. Switch the phase on one, and the bass is back.
If they are mounted/non-moveable speakers, you can still get the "weird" effect by carefully positioning yourself in what would normally be the "sweet spot", and then move side-side a little. The effect should be unmistakable.