We have visited South America many times in the past 14 years.
You refer to Winter, I assume you reference Winter in North America.
Uruguay, Argentina and Chile are great and it would be their Summer when you visit.
Those countries a much more like Europe than the rest of South America.
Recommend a two week cruise around Cape Horn from Buenos Aires to Chile or in reverse.
All those countries have plenty of English speakers.
I don't recommend just staying in one town or city. There is a lot to see in all three countries. Santiago, Chile is worth 4-5 days. Valparaíso is an interesting city on the coast.
Other great countries to visit are Peru and Ecuador.
Ecuador has Quito, its capital which has much history, but also it has part of the Amazon as does Peru to visit. The greatest thing to see in Ecuador is the Galapagos Islands, which are very, very special, but most tours there are expensive. Gate 1 Travel has a good tour of Ecuador that does three nights in those islands. We did a cruise for a week that was fantastic, but expensive.
Peru is our favorite S. American country. The cuisine there is very special and excellent. Lima is worth 3-4 days and has much history.
The best part of Peru is south including Cusco, the former Incan Empire's capital and worth 2-3 days. Then on to the Sacred Valley toward Machu Picchu. Do a tour that includes this and Machu Picchu. It is amazing. Machu Picchu is a complete Incan city almost intact that was only rediscovered a little over a hundred years ago. We used a great tour company called PeruAgency.com for our four day tour of that area and the cost was very inexpensive.
One thing about visiting Peru and Ecuador, is don't go during the rainy season, which would include much of the months of Jan-March.
Go in April or May.