Thanks for your thoughts and advice.
We booked the exec room/brkfst package for the same price as what their standard room is going for now. It was a great deal offered on Hilton.com several months ago and we grabbed it. They recently had quite a price increase, so needless to say, we made an excellent move while guaranteeing an executive room and daily breakfast buffet.
Just curious if anyone has had luck getting upgraded from exec rooms to higher categories. The BA Hilton has 3 room types above the regular exec rooms. Who knows, maybe we will get lucky, but probably not. Either way, I can't wait to see Buenos Aires.