Mar Del Plata is really a city -- 500,000+ people in the off season. It will be mobbed when you want to go. The beaches are crowded and very commercial (like a collegiate Spring Break but for adults -- there's Visa beach, Quilmes (Beer) beach, etc., and the beaches are covered with rows of rented huts). It's not very international, so you might struggle if no one in your family speaks Spanish.

Punta del Este is the upscale Argentine's choice for vacation. A Hamptons-like scene. For an American it doesn't seem like a great value -- their high season lasts only 10 weeks, and local businesses really gouge the visitors from Xmas until March 1. The people who are there (and there are lots of them) really feel like they have to be there and no place else.

Brazil really is the place to go. Not just for scenery, but for a cultural experience.

Florianopolis has about 30 beaches, each a bit different, and most have some level of development (hotels, restaurants). We last went there in March 1999, and we found it to be a tough place to research -- use the internet (check the island, not the city of Florianopolis) and a Brazilian travel agent (lots in NYC). Each beach seems to have a different personality, in terms of the types of hotels/resorts and the types of crowds they attract -- Argentines, Brazilians, Europeans, Young, Old. It's the closest Brazilian beach resort area to Argentina, so it's popular with Argentines. We reserved a place on a north side bay called Canasvieiras, and found it inadequate -- so we stayed that night, checked out, and drove down the road until we found a place we liked better -- suprisingly simple to do. I'm not sure I'd recommend that for Xmas week. There is a huge condominium resort that takes up a whole beach on the south side -- not sure of the name -- but it seemed to be a high quality place, in Naufragados or Pantano do Sul.

Having said all that, I think Buzios is a better place. It's not as crowded after Christmas -- since it's north of Rio (i.e. warmer), people think of it as a place to go befor Christmas -- Just like Americans from the north don't go to Florida in July. Again, you might enjoy a day or 2 in Rio mixed with time in Buzios.

For Florianoplis, you'd probably fly to Sao Paolo -- more flights than Rio, but you would never want to spend time as tourists in Sao Paolo.

Good Hotel with suites and apartments in Buzios -- La Boheme (www.labohmemhotel.com). Cigalon is a good restaurant, right on the beach. Brigitta's is a great restaurant. Kayaking and Diving are easy to do there. You can check www.buziosonline.com.br Have the travel agent arrange vans between Rio and Buzios. Taxis are plentiful, cheap, and safe in both Buzios and Rio.

I guess you can see my biases. Have a great trip -- wherever you go!