We propose local mechanisms for efficiently marking the broader network region around obstacles, for data propagation to early enough avoid them towards near-optimal routing paths. In particular, our methods perform an online identification of sensors lying near obstacle boundaries, which then appropriately emit beacon messages in the network towards establishing efficient obstacle avoidance paths. We provide a variety of beacon dissemination schemes that satisfy different trade-offs between protocol overhead and performance. Compared to greedy, face routing and trustbased methods in the state of the art, our methods achieve significantly shorter propagation paths, while introducing much lower overhead and converging faster to near-optimality.