In this work, we consider the problem of coordinating the motion of a platoon of unicycle robots navigating inside an obstacle-cluttered workspace. We assume that each robot is equipped with on-board sensors that allow it to perceive nearby obstacles and obtain its relative position with respect to its preceding robot. Additionally, no robot other than the leader of the team is able to localize itself within the workspace and no centralized communication network exists, i.e., explicit information exchange between the agents is unavailable. To tackle this problem, we adopt a leader-follower architecture and propose a novel, decentralized control law for each robot-follower, based on the Prescribed Performance Control method, which guarantees collision-free tracking and visual connectivity maintenance by ensuring that each follower maintains its predecessor within its camera field of view while keeping static obstacles out of the line of sight for all times. Finally, we verify the efficacy of the proposed control scheme through simulations.