I took lessons for many years... starting out is fine if you've got a sense of rhythm and you can "feel" in your body that you know what the music is supposed to sound like when you play it. Shouldn't be a problem since you're wanting to learn Coldplay songs and you probably know how they all sound by heart, right? ;) If Coldplay songs are all you're planning to learn (instead of, say, classical stuff) then just download the chords or guitar tab and have a piano-playing friend teach you the chords on the piano. You don't even need to learn how to read staff music unless you want to.
Hope that helps! :D
<>< M