Well, Curitiba is the best city to live in Brazil. you don't worry about don't speak portuguese. We, Brazilian, speak English. We don't speak fluently , but we can always help using basic English. Where will you stay: homestay, or hotel or University houses (I think is the name!?!?!?!)?
The winter in Curitiba is very cold, but depend... Where are you from? The weather is between 8 or 9 degree until 13 or 15 degree.
I don't think that very expansive live in Curitiba. Today US$ 1.00 = R$ 1,75. I suggest that you cook your food. We eat simple foods: rice, bean, steak, milk, bread, green salad, vegetable and fruits. But we have McDonalds, PizzaHut and other places. I would like to suggest that you eat our pizza and visit a barbecue house. It is wonderful!!!! I don't know about capoeira. Sorry! If you were study in Sao Paulo, I could help you and show the city. You can visit the sites: www.paranaturismo.com.br, www.paranacidade.org.br, www.ufpr.br (oficial site of university). I wish that help you.