The incubation period for smallpox is roughly 12-14 days. The smallpox vaccine is considered effective administered up to five days following exposure (before the rash appears).
Interesting reading: The Vaccine Reaction--What Every American Needs to Know
Considering that the government cannot even manage to send bullets with the national guard (LA riots), I wouldn't trust them to get vaccines to us within 5 days of exposure.
Best to be prepared - that means get vaccinated ahead of time.