Okay, let's remove some of the gray area now. Since the original premise was "bug out or seek public shelter", let's assume that we are already prepared for an emergency where the normal conveniences are no longer available. That means no municpal water, no electricity, no natural gas, no gas at the pumps, and limited consumable supplies. Okay, most of us can plan for that kind of event, and assuming TEOTWAWKI hasn't occured, we can expect that within two weeks relief will be available. So the "temporary isolation" scenario is not a factor.

But let's suppose something happens that generates a persistent, chronic threat. It could be some exotic disease, or some form of contamination, or maybe just a regional civil unrest or (gulp) invasion. Now this presents conditions that make sheltering in place less desirable. We can, of course prepare for these more dramatic but less likely possibilities, though at considerably greater expense. Nonetheless, these are real risks, which would make normal survival efforts much more complicated if we remain in the area of effect. So the question then will be just how effective is going to a public shelter within or near the area of effect, as opposed to migrating far enough away from the affected area to eliminate significant risk. To my way of thinking, staying near the risk zone is not advisable, no matter what municipal support may be present. Sheltering in place under these conditions doesn't make much sense either. The only logical conclusion is to move somewhere away from the threat.

So now that we've clarified under what conditions we should take flight, the idea of going to a public shelter is only for those who are truly unprepared for life's more mundane hardships, like floods, fires, storms, earthquakes, and such. Sure, these events can lead to bigger problems such as I pointed out earlier, but for situations where the only threat is the loss of utility service or supplies for a limited time, there's just no reason to leave home for that sort of problem. If things ever get bad enough that home is no longer safe, then likely no public shelter nearby is going to be any better.

For instance, when Katrina hit, people fled their homes for public shelter to escape a significant threat. Anyone remember what happened to the superdome during the storm? That was supposed to be a public shelter, right? It sure didn't look very secure to me when the storm came in through the top.