The facility is operated by Portland radio cab,primarily as a benefit for the taxi drivers. However, the facility is open to the public, though it is almost completely unadvertised.
The official address is 1613 NW Kearny, but the entrance to the gas station is off of 16th avenue (see photo 1), right by the sign that advertises gas prices (see photo 2). The nearest I-405 freeway exit/entrances are 2A and 2B, which are only several blocks away. Lovejoy street (1 block north) is a major east-west road due to its connection with Cornell Road, which goes over the hill to Beaverton.
The prices charged are not necessarily better than the rest of Portland, but sometimes they may be. You will certainly find that it isn't worthwhile to drive a vast distance out of your way.
However, if you are passing through Northwest Portland and need to get gas, then it might be worthwhile driving past to see what the prices are and how they compare to the rest of Portland (especially downtown Portland, which tends to be high anyway).

