Have you already been? This info may be irrelevant but will leave in case others ask.
9pm or later from Cordoba straight up Alvarez Thomas to Triunvirato and Congreso takes less than 20 mins -- last time I took a cab was a couple of months ago and it cost about 35pesos -- not sure if there's been another increase in fares since then, and it was summer when there's noooo traffic. The moment you get stuck at one of the two railway crossings you go past, it can easily double. There is always a mess of traffic up until about Lacroze.
Whereabouts in Palermo are you leaving from and whereabouts in Urquiza are you going to (Urquiza is big)? The B subte you have to get on at Corrientes (there's stations at Malabia, Dorrego, Lacroze), it drops you at Triunvirato, you can exit either Monroe or Roosevelt. The train from Carranza to Urquiza takes 20-25mins and drops you on Monroe and Bucarelli currently (they are redoing the station). The other option is to take the D to Congreso de Tucuman and then get in a cab down either Monroe or Congreso (Monroe tends to be faster right now as there's no construction).
Assuming you're coming from Palermo Hollywood, if you are going at a busy time of day, I'd really recommend the train or subte. Not because I'm being stingy, just because It is so much faster. I have a car but often take public transport from Urquiza simply because of time saved. With congestion in the middle of the day or rush hour you could easily sit in traffic for 45mins or more.