While you cannot reset just the guitar preset settings on the Play Acoustic, you can always manually adjust the presets back to default. The following are the four Guitar FX screens with default parameters on the Play Acoustic.

To reset all of your Play Acoustic's presets back to default, when powering up the unit, press and hold the two arrow buttons next to the Control Knob. Any changes you have made to presets will be erased and will revert to factory defaults.