"...a connect speed of 54 mbps... it is rated at 150 mbps"
Although the adapter is 802.11n and rated at 150Mbps, it will only connect at this speed if the router is also 802.11n. The connection speed of an 802.11g router is 54Mbps.
However, it is your internet download speed that you need to check. Go to the Speedtest.net site and run a test to see what speed you're getting.