Hola from Uruguay!
I used a really cool fast boat to get to Colonia from Buenos Aires, called "Seacat". It only takes an hour, and you're in the lovely pastoral colonial little village called Colonia.
The village is very beautiful and is in fact a resort for tourists from all over the world, but also for people from Argentina and Uruguay.
It's incredibely hot, so luckily there are many beaches where you can cool down... Night life are extremely different from Buenos Aires, and are a bit more "normal".
Restaurants serve dinners around 20:00 until about 23:00, and the bars close early during weekdays... Like I said - a good place to run away from the party life of BA and rest a bit.

I spent 2.5 days here, definately enough if you just want to catch your breath, visit another country and get some sun on the beach. Had some good Uruguayan grill, great Ice cream and a lot of tan ;)

Back to BA to the parties and drinking... Here we go again! :D

Gilad.