I am a little surprised that guitar instruction books would even mention modes. I have suggested the theory that the introduction of the guitar into southern mountain music was one of the things that contributed to the decline in the use of modes. So far that theory seems to be ignored in discussions of modes and perhaps for good reason. When vocal music, the banjo, and fiddle were the primary elements of mountain, traditional music, the emphasis was on melody and in traditional music that was generally melodies based on modal scales. The introduction of the guitar to southern mountain music around the turn of the twentieth century brought about strong chordal possibilites and a shift away from modal scales and open tunings to a standard tuning and the now commonly accepted major scale. Here in the Ozarks, that was also a way the "young folks" could make the archaic music of their parents a little more "uptown". I suspect that most guitarists who have any interest in modes play a lot in open tunings. As for your playing with people who announce that a particular tune is in "such and such" mode that would mean you would look for a few unusual chord changes. As was stated earlier the only modes you are likely to encounter are Aeolian, the minor mode, Dorian, a mixture of major and minor sounds and Mixolydian, which means if you are in the key of G you will need an F chord somewhere before the tune is over.