Yes, you are suppose to meet Talana and have a cutscene as you enter the full Broken Valley. This gives you the next main plot quest, but does not prevent you from returning or finishing off quests in the starting section.
There are a couple places like that in the game, though, the first there is a warning about in-game (the final section of taking over the battle tower, at a character level in the high teens or early twenties), and the second should be obvious. In the first case there are a couple quests that must wait until after that point, but other than that most areas and NPCs will no longer be available in the first couple map areas.
