A concept of Cloud Radio Access Networks (C-RANs) with Power over Fiber (PoF) is expected to work as a post- disaster access network architecture. In this architecture, since external power is supplied to Remote Radio Heads (RRHs) through the optical-fiber cable for data communication, RRHs can operate even when power cables are disrupted due to disasters. This network, however, needs to reduce the power consumption for RRH operation and consider Quality of Experience (QoE) to provide sustainable service with enough user satisfaction. To this end, we propose user position guidance approaches which give advices of the best position to users. Our proposed approaches are able to achieve high sustainability while satisfying the QoE constraint. Furthermore, the effectiveness of our proposed approaches is evaluated by numerical calculation.