i rode a 12-26 for years living in SD (rancho penasquitos area). i didn't move to a 27 until i moved into east county and started riding the foothills. most riding west of there isn't too gnarly. i think you'd be fine without a climbing set up, though, it wouldn't hurt, since i'm sure you'll want to go east - even though it will be hot as hades in east county in the summer.