but it only will get 11mbps,

And your wireless adapter have nothing to do with your son PS2.

I quote:
== "It says that 802.11b is compatible with 802.11g. Is this true?" ==

NO! but, 802.11g is compatible with 802.11b ..

The G system can transmit/receive to/from B system

Or

The G system can work as B system (11mbps)
The B system CAN NOT work as G system (54mbps)