Assuming that you're talking about the sign, I found another just south of Sunset on Highland Avenue. As both Vine and Highland are southern approaches to freeway intersections, my guess would be freeway information signs, but that might just be because I'm remembering Steve Martin in 'LA Story'.
GSV
BTW
Martin Pal,
t2's picture also shows the two towers we've been discussing. The one on the left (the Sunset Vine Tower) is on the south side of Sunset.