“Sign, sign, everywhere a sign. Blocking out the scenery breaking my mind …” Artifacts hates that dumb song, in no small part because we’ve always rather enjoyed signs, from the handpainted storefronts of the West Side, to the (now-extinct) revolving Butter-Krust billboard on San Pedro just north of Hildebrand, to that maddeningly infectious Clark Gesner song-and-video from PBS’s “Electric Company” (“I like fish food, you do too/ Don’t look now your hair is blue … ” Remember that? You can find it at http://www.youtube.com/watch?v=23tIhD3Lw-Q.) But we digress. Opening this Friday evening is Unit B’s CAM offering, a supergroup show called Let This Be a Sign. For this exhibition, sign recycler/appropriator Gary Sweeney is de trop, of course; his signage collage at SAMA and his hilarious “advertisements” at the airport being only two examples of a career-long meditation on the medium. And Alejandro Diaz, whose neon musings and subversive product placement bridge the distance between writing and architecture, certainly fits the bill. But given Kristy Perez’s recent ballsy declaration at Sala Diaz `see “Have we already arrived at ecstasy?”, July 8`, we’re looking forward to seeing what in the world she’ll be spelling out this time.