When you get to Lions Arch, find a runner back to Ascalon, or run yourself with heroes. After the heroes update in Nightfall, every character can run as long as his heroes are properly set up.
Route is via Northern Kryta, Scoundrels Rise etc towards Beacons Perch. From there, go north to the Ice Cave town, from here go east over the northernmost slopes of the shiverpeaks, all the way to Yaks Bend. Take from Yaks a route to the south, across the Ascalon Foothills and keep going east through to Grenths Courthouse and from there you can go through the Breach in the wall. On the east side of this map lies Ascalon City.