Surfer can grid or plot any numeric values for the X and Y coordinates. Latitude and longitude are fine as long as they are in decimal degrees. Longitudes in the Western Hemisphere and latitudes in the Southern Hemisphere should be expressed as negative numbers.
If your latitude and longitude values are not in decimal degrees, you can follow the instructions here to convert the values to decimal degrees: https://goldensoftwaresupport.zendesk.com/knowledge/articles/226662488.
Updated September 12, 2017