Buenos Aires: Day trip to Colona, Uruguay
 

Based on recommendations on this site, we would like to take a day trip to Colona. I have checked the buquebus website but not knowing Spanish, I can't determine if reservations are necessary. Also, there seems to be only one boat. Would we be OK just going to the dock first thing on a week-day morning (sometime between Feb 14 and Feb18)? Will we need to get Uruguay currency when we arrive or would $US or Argentine pesos be accepted? Thanks to everyone who has been so helpful with my questions to date.

I don't think it is necessary to make a reservation...I did not and had no problem. Most people did not have reservations.

You can use Argentine Pesos or $US in Uraguay. I found that the rate of exchange with the Peso was very fair and there was no need to exchange money. You will need to pay a small departure tax when you leave. Use whatever Uraguay money you have received in change to pay all or part of this.
It is simple to walk into the town from the Ferry dock...not too far if you are not loaded down.

After thinking about it, I remember that I did go to a Buquebus office in BA and bought tickets a day or so in advance.

There are several offices around BA and your hotel can direct you to one.

There are several boats to Colonia. However, if you are just going for the day, it's best to get the high-speed ferry, rather than spending a lot of time going and coming. The ride is really not very scenic, so faster is better. We did not find it necessary to get Uruguay currency. They are used to dealing with Argentine Pesos, and you will be surprised at the many places that your USD are accepted. As for reservations, if you are around the Puerto Madero Area touring, you can stop by the Buquebus Office in advance to save stading in that line the morning of your travel. Porte Madero is worth the walk...you can stop at one of the many cafes, have an ice cream, or just admire the view of the Caltrava Bridge. Remember to walk across the bridge for a stunning view of the City's architecture.

Sometimes the boats, especially the fast one, sell out a few days in advance. As someone who rode the slow one, I would definitely opt for the high speed option. No problem with using the argentine peso.