Yes, the BEFW11S4 will work fine with a PS2. Just use the PS2's network setup disk and tell it to get all its setting automatically (DHCP). I've not used the disk in a while, but I think if you just leave all the settings on their default then you'll be configuring what you need (all automatic settings).
At one point I had one PS2 directly connected to the router, and another connected via cable to an iBook which was sharing its wireless connection to the router with the PS2. My ex-housemate and I were trialling PS2 network games (we work for SCEE)
