Given the topography of the proposed area in which Alma's group would be traveling, it is of no surprise whatsoever that this people should find themselves in a valley. This area is a maze of mountains and valleys, and as has been previously noted, is one of the explanations for the multiple peoples passing through the same general area, but not easily finding each other.
The naming of the valley Alma is certainly more symbolic than permanent, and this people intends to push on. Putting down permanent roots only a single day away from their oppressors would be incredible folly, and we may be sure that they never considered it. Nevertheless, the naming of the valley with Alma's name reconfirms his leadership of the group, and stands as a reminder of the more interesting naming of the area and city of Helam from which they have just fled.