Depends on whats happening. You have to have flexibility in your plans. Is it something limited to your city? Is it nationwide? Contagious? Riots? Fires, Earthquake? I guess it would be good to come up with some categories of threats. If you had to evacuate your city, would the roads be clogged? Are there alternate routes out? Is the cell network up?

I live in the boondocks, so my inclination is to bug in, but if I had to load up the vehicles and get out I could. I'm trying to make sure everything I need is portable, anyway. I don't know where I'd go, probably west into the mountains.