Au contraire.
Walling off a major city like NYFC won't be up to Hizzoner, or even Governor Five Families.
It will be up to the 20 contiguous mayors and counties, who'll all cut NYFC off without a second thought, and stand off all comers at gunpoint.
Ebola hits Manhattan, and that order's going out in about a NY Minute.
Once the pile of bodies testing that resolve get to be a couple of feet high, you won't be able to get anything in over the speed bump it makes.
The bigger problem will be seeing to it that some number of infected people don't crowd onto every airliner and private plane trying to queue up and depart in haste.
That's generally the point at which F-15s with warshots and simple but brutal no-fly ROEs settle things down rather rapidly.
The issue here isn't how much it will spread, it will be how long before those with the authority to declare a quarantine wait until they do it.
Given the lack of adult supervision manifest in DC for the last 5 yeas, I figure everyplace is pretty much screwed until governor and mayors independently decide "F**K D.C., the quarantine order goes out now!"
Current sensibilities argue that will happen in about 5 minutes after an outbreak is declared anyplace, which is why the main role of the CDC here is going to be to lie and deny for as long as possible, to give HopeyDopey maximum time to dither before he finally suits up.
Which could kill you (and a few million of your friends and neighbors) come the day.
*(L.A., same same. The county is surrounded by generally brighter (and redder) counties, who'll shut L.A. County down in about as long as it takes to barricade freeways and exits. There are less than a dozen freeways involved, which will go fast, then the surface streets, which will take longer. But if you shut down Pacific Coast Highway, US 101, I-5/405, and I-10, the entire L.A. megalopolis is functionally isolated. And the west, north, and south helpfully travel through impassible mountains with little to no side road access, and the east is hundreds of miles of desert. And when the smaller communities bordering L.A. Cirty, and those bordering L.A. County are given the choice, the curtain will come down, and ain't nobody getting anywhere, unless you have a longe-range boat or light plane nearby, and go before the FAA issues no-fly orders, and the USCG gets into the act. Max, you've got an hour, maybe three, and then where you are is where you'll be. For those who think they'll sail away, take a wild guess how long the quarantine will be anywhere you land, unless your documented voyage took longer than 21 days. At that point, you're better off just sailing up and down the coast, or anchoring in the lee of the Channel Islands, and learning to enjoy a seafood diet. All of the benefits, none of the pitfalls of the open sea, and a helluva lot less piracy and government gunboats to deal with. Hopefully.)
All things being equal, I'd be wishful instead of having a couple of ISO conex boxes buried on a semi-rural piece of land, with a well (or at least a cistern) and a couple/few solar panels.