I think you should register to vote anyway, even if you don't spend much time at home. Then, you can become an Absentee voter. I think you just go online and got a form to fill out that you then mail in.

That way, even though you can skip the local stuff you're uninformed about (though there are often propositions you can figure out for yourself) you can still vote for (or against) people for President.

I'm an Absentee voter even though I live a block from my polling place. It's the greatest thing in the world, and I recommend it for everyone. No lines! No trying to fit it into your busy schedule! It's easy and fun. As they say: Vote early, Vote often.