An implanted fluid access port locator system for adjustable gastric bands. The system may include an access port having an RFID tag with its antenna adjacent to the receiving portion of the port. An external locator with radio frequency transmitter/receiver circuitry sends read or interrogation signals to the RFID tag and may send write signals to the tag to write treatment data to memory of the RFID tag. The locator may include an antenna array with four patch antenna arranged in pairs to model two monopulse radar antenna systems. The locator also includes processor(s) and logic modules/circuitry for processing the tag response signals received by the antenna array to determine location information for the RFID tag and associated port, i.e., to identify the center of the port relative to the antennae array or array face such as with strength and direction information relative to the array face. A method of locating implanted fluid access port includes providing radio frequency transmitter/receiver circuitry on the access port and manipulating a handheld locator outside the body to pinpoint the position and orientation of the access port. A mark may be made with a handheld locator to direct insertion of a needle for adding or removing fluid from an implanted system through the access port.