How long is a piece of string.
As steve says for airmail, assuming there are no delays, and it's not slowed at customs then 3-5 working days for airmail, however I have known it to take much much longer, especially if there is any sort of delay at customs (they run a first in, last out system, so anything that arrives at the start of any delay will be amongst the last out).
If it's not airmail, but priority surface (surface/airlift) which uses surface transport where possible, but aircraft for the ocean part of the journey (which might take it as far as France etc depending on the cheapest router) then anything from 3 days to about 4 weeks.
Surface mail, anything from about 2 weeks to 2 months depending on how many times the ship gets boarded by pirates