yep. that's where I was thinking. i agree that the best areas for food trucks are typically dense office areas or special occasion areas. i work near hospital hill and am pleased with the turnout of both food trucks and patrons. similarly happy during first weekends in the bottoms. when i worked in the government district off of 13th street, i enjoyed the random few days when food trucks would station outside the Inter-State Building. would always remind me how a decent lunch-oriented restaurant might do well in that spot.
my thoughts for Armour Blvd was based off of pure experimentation. good for evenings as it's a fairly populated residential area. Armour is also a really wide street with street traffic that never, anecdotally (via walking) seems to be that bad. it's also, as far as food/retail options go, kind of a desert, with martini corner being the nearest area for better-than-burger-king eats. all of this, i'm sure you know. my other thought was...not excellent delivery options in the city. if i were running a food truck i might think about how i could do hospital hill for lunch, armour for dinner, and westport/crossroads/pnl for late night. but i don't operate a food truck, and there is probably a good reason for that!