From what I read, Bonnie, you don't seem to have real desire to learn vocals. The motivation appears to be responding to comments from others rather than a fire from within. It doesn't strike me as a compelling reason to add singing/learning words to your repertoire.

I do like to sing, and learned guitar chords to be able to accompany myself singing. That way I could be sure the guitarist (me) would be able to do (most of) the songs I wanted to sing. As I have no real interest in writing songs, and you presumably have less interest in that, I can't help but wonder what the value would be for you in a songwriting class.

You may find that singing to some of the songs you play will help in developing your instrumental skills, especially if you plan to play while the songs are being sung by someone. In particular, elements of phrasing and timing might be affected by this. Examples: Sometimes a singer needs a few extra seconds to remember the words to the next verse, having the instrument players repeat the opening line rather than plunge into the whole verse can be helpful. Some songs, when sung, have a "pause" measure that is often left out by instrumentalists--singers are accutely aware of this but many pickers have never even thought about it. Some songs have vocal "dead space" between lines that are perfect for fill-in riffs, obviously one has to know how the singing goes in order to identify these.

Now, is the real question one of trying to figure out if you want to do vocals, or trying to figure out what to say to folks who tell you should do them?