Daytrip to Montevideo

It's not especially interesting, in my opinion. If you like classical music you might make arrangements to attend a concert at the recently re-opened Teatro Solis. Also you might combine Montevideo with a trip to Punta del Este.
I think it is worthy staying 2 days (1 night)... why not.
The historical center of Montevideo is a place of architectural beauty.
Visiting the harbour market and drink a medio y medio can be a nice plan for midday.
During the weekend they have a quaint antique fair, I guess is on Sunday. Also on Sat. and Sun. in front of the History musuem there is a handycraft fair. In my opinion pottery in Uruguay is the best!
Besides Montevideo has beautiful and wide parks, slower traffic and more polite people (it is a shame but I have to admite it).
Hope you like it.
montevideo is great, like buenos aires on sea but much more chilled out. the Sunday outdoor market is one of the best i've been to anywhere in the world, the beach (i can't remember the name of the neighbourhood but it's the 2nd beach along from the city centre) is great-all white sand and you can swim as well in the sea/river. there's some incredible architecture. the views from the old fort are lovely and the people are unbelievably friendly. and i haven't even mentioned the chivito canadiense...the nightlife is not that exciting but it's a great place to go if you just want to chill for a few days. it's a pretty safe city as well, certainly no more dangerous than BA (assuming you don't go wandering around dodgy areas).
if you've got a little cash then stay a couple of nights at the hotel plaza fuerte in the old town, a beautiful restored old mansion. you can book a package through buquebus which usually works out cheaper than booking separately.
I just got back from Montevideo and I have to say that I was surprised. I had a great time there. I was only planning to stay 4 days but I added a fifth and still felt like it wasn't enough time. I would say that if you are a guidebook, have to see all of the "approved sights" , need to be running around chasing some monument all of the time type tourist you will be disapointed. Most of the tourist attractions that you hear about in Montevideo are worth a look but don't get your hopes up. Unless you are a Historian or something many of them merit a glance and then you move on. (Although a couple of sites that really were interesting to me were the housing projects near the dock by the old city which suddenly made me feel like I had teleported from Colonial times to the South Side of Chicago and the old cannon turrets with grafitti all over them. They seemed to be keeping watch on the harbour like someones old, wrinkled, wheelchair bound grandfather watching the action in the street in front of him. These sites were not listed in the tour books but were a lot more interesting to me than what was) It is a great place to walk and relax though and just unwind a bit. There is this amazing breeze that flows through the city at all times that seems to be telling you, "Relax and take it easy." During the day you welcome it on the beach as the sun is blazing down on you and the breeze evaporates the water on your body from intermitent dips in the ocean. At night it becomes a bit stronger and you can dress up comfortably in slacks and a nice shirt for a night on the town without baking to death. I stayed in an area called Pocitos and it had a certain quality that I loved but is hard to describe. It sort of reminded me of a mix of the best of Rio and Sao Paulo mixed together with a splash of Buenos Aires but much smaller and slower. Montevideo is very relaxed but everything is still there. They are showing all of the movies that are just coming out in the U.S. and Europe and they have really nice shops and restaurants. I ate at a great Asian fusion restaurant called Tandor. The food was fantastic but the guy is almost going out of business because the Argentines and Uruguayans just want beef and Italian food. I just went there to renew my Visa but the place just had so much to offer that I will be returning at the end of February. Now that I 've done the obligatory sight seeing I'm sure that I'll have a better time relaxing on the beach and doing some shopping.
Ciudad vieja is great from wednesday untill saturday if you want to eat something and get a beer. Lot's of people
I have to say I love Montevideo and it has a unique charm that grows on you.
The archictecture is very interesting and varied and the nightlife while small is vibrant. I also love the town of Fray Bentos which few tourists visit . I suggest that you give this place a look its very pleasant