Name a really good alternative rock song for me to learn to play?

Yeah, Coldplay's Scientist would make an interesting acoustic guitar cover, since the regular version is piano-based. You should also hear the acoustic version of Yellow. That can also be played solo.

Also: Radiohead - True Love Waits, High and Dry, Fake Plastic Trees
Oasis- Wonderwall

something by coldplay

311 - Electricity

Anything by Oasis is good if you're starting out. "Don't Look Back in Anger" and "Wonderwall."

Superdrag is another good band for learning chord changes and transitions. "Sucked Out" and "Do The Vampire."

The Lemonheads is another good one. "Confetti" and "My Drug Buddy."

All of these songs can be played nicely on both acoustic and electric guitar.

Rock on bro. I learned on these songs myself.