Some choose to not worry - if something happens then they say it's their time to go.
Others continue their day-to-day activities, but are slightly more cautious of their surroundings.
Others are more drastic and are moving to different areas that may be of less risk.
I think it's up to you to decide what's best for you. If you're constantly worrying about your safety, then maybe you should consider relocating to a different area where you'd feel safer. I don't think there's anything wrong with that at all. If you feel that it's your time to go if something happens now, then....stay.
Just know the threat is real. There are thousands of people in the Middle East that live each day plotting how to bring the USA down. They are intent on causing USA casualties, and it only stands to reason they will succeed in some way at some point in time. These are the harsh realities of life today, in this country and any other Ally unfortunately.
Personally, another catastrophe and I'm outta here. I'd rather not have to deal with the potential chaos that could break out in this country. I don't feel my time is up yet, and I'd rather not have it cut short prematurely because some people want to make us pay for our governments actions.
I'm not interested in street violence and gangs, therefore I don't live in a neighborhood that has that type life prevalent.
I don't smoke, therefore I don't hang out at smoke palors.
I don't desire to fall sick due to some disease such as anthrax or smallpox, therefore I will take any measure necessary to prevent that from happening. If it means potentially moving to another part of the world, then so be it. There's so much to see, I have no reason to limit myself to one particular area for the rest of my life anyways. Picking up and relocating will not be an easy task, but it could be done if I felt my life depended on it.
I think the wise person would consider these things now and have some sort of "just in case" plan in mind, for our lives could change any day now. I've had several events happen in my post-JW life that happened because I was not wise enough to look ahead and see the outcome of my actions. After all of the events, I wish I had followed my gut feeling, because it was talking to me, but I ignored it. Same applies to now - I have the same gut feeling...but I guess I'm waiting for the first bad thing to happen before making a decision.
Hopefully that first bad thing won't be the nuke in San Fran. :-P