Songster Bob, you might also want to include the House of Musical Traditions (HMT to the cognosenti). Their prices are a bit high, but they usually have a good selection of guitars as well as many varied instruments (from sitars to djembes to tongue drums to a massive number of accordians).

Located in the center to Tacoma Park, they used to reside out in Berkely Springs, WV. I now make a pilgrimage once or twice a year (as well as to Chuck Levins - RIP). Dave Eisner is the owner and personally knows almost any of the folkies that count, (having booked them for his own concert series). And his current general manager, sings with the Pyrates Royale. The best I can say about the place is that they will break up a package of Autoharp strings, just to sell you the one you need...

As for Chuch Levins, you have to know what you want before you set foot in the store, because the atmosphere is somewhere between a Jewish wedding and the Fall of Saigon. But there are no cheaper prices anywhere...