Data communications are selectively routed via an appropriate wireless access network including wireless cellular networks and wireless LAN, according to presence status of a mobile station. A network system tracks the presence status of the mobile station, which may relate to its availability and willingness to communicate via a particular type of wireless access network such as wireless LAN. With this kind of presence status information for a mobile station as guidance for traffic routing, inbound data communication can be routed to, and outbound data communication can be sent from, the mobile station, all via the desired access network. When applied to wireless LAN such as Wi-Fi network, this presence based routing mechanism can effectively reduce traffic burden over the wireless cellular network for the wireless carriers while lowering the cost of communication for the end users under usage based data plans.