Nice report, looking forward to reading the rest.
The "cubierto" charge is typical in the Southern Cone and in some parts of Southern Europe (I've been charged "coperto" in Italy as well). It's basically cutlery + bread basket. Not that you can refuse it, though. Some places have huge signs "We don't charge cubierto", but those are usually on the less exclusive side. I guess I'm used to it as a local, but it seems just as silly as the 20% tip they have in the US, which gets on my nerves every time I visit
I agree with your impressions about Montevideo. The Francisco ferry is allegedly a green vessel, hence they make you wear the silly things over your shoes. Sounds a bit too much, but oh well, it's the fastest way to get to Montevideo from BA.