http://en.wikipedia.org/wiki/Wormhole would seem to indicate that there's a non-zero travel time through one.

> However, in 1962 John A. Wheeler and Robert W. Fuller published a paper showing that this type of wormhole is unstable if it connects two parts of the same universe, and that it will pinch off too quickly for light (or any particle moving slower than light) that falls in from one exterior region to make it to the other exterior region.