In a pinch (IE you gotta get somewhere cause your not really prepared) some of the deeper abandon mines in our area could suffice , or at least be better than nothing.
Such mines are scattered everywhere in this state.although you still need to worry about food and water , and because you need ventilation they won't be perfect.
Certain vitamin and mineral suppliments can be used to avoid contamination to an extent,such as calcium ( competes with cesium for room in the body) and pottasium (can't remember off the top of my head,but works on another typical radio toxin).
Your basement can work , but you need to make extensive modifications you won't have time to do on the fly.