So we did end up trying Agua Ardiente on Friday (24th Street NW between M and N, near the World Wildlife Fund).
It has just about the same menu (as I remember it) as Gua Rapo, but the wine list is far worse. This is inexplicable, as it is supposed to be the larger and more restaurant-y of the two. One non-chardonnnay white, which ran out after my first glass. Reds run to grocery store options.
We ordered a lot of food since we were trying it out for a function. So there's a lot to review:
Generally, too many fried plantains. They were all over the place--side, garnish, etc.--on just about every dish but the salads.
The stars were the ground beef empanada (nicely spiced, good crust) and the tuna ceviche (gained a little something from the sesame oil). The fried calamari was nice and light. We did not try the salads, but they looked very good. I didn't try them because I had confidence in them based on the ingredients. This may have been foolhardy.
The salmon was quite nice--had a good spicy rub on it. Came with the ubiquitous fried plantains and a good sauteed corn with little diced vegetables--peppers, tomatoes, etc.
The llingpachao advertised three cheeses inside, but there was only one. It was also so gooey I felt like a dog with taffy in its mouth. It is not a potato cake in the sense that I was imagining (i.e., shredded) but like mashed potatoes (tasting suspiciously like a cafeteria's) surrounding a glob of gooey cheese.
The tamal was also odd. (Californian fiance did not get his hopes up, but I did.) The surrounding corn was not grainy, but more like corn pudding. The meat was good, but that surrounding corn spoiled the experience.
The churrasco was a sub-par cut. Very gristly. The "steak knife" had no effect on certain portions. The only option would have been to pick it up and gnaw.
We sat on the upstairs (street-level) patio. It is on a nice quiet block, and it was a pleasant evening, so it was a good experience overall. If it had been hotter, the *very slow* service would have made me cranky. Of course, we also had plenty of food to keep us occupied.
Function rooms are sort of fun--they are very South American Gothic. Red velvet curtains, icons, etc. The function manager is very friendly and helpful, which is also a nice change.