I placed a limit that say, 12,000 men can make it in four days from Highgarden to KL, I would say that if you were to muster perhaps 50,000, or approximately the rest of the Reach's forces, about two weeks- which I would imagine is the same for the Westerlands. Two from Tumbleton, or just under. If Garland was alone, he could ride from Highgarden to KL in probably two days, if he was fucking hoofing it.