I've spent a fair amount of time in Brasil and my choice would be the NE around the area of Natal south and Maceio north. There's clearly a more European feel in the south around Porto Alegre and RS but I prefer the atmosphere of the NE.
Buying property used to be very complicated if you aren't Brazilian and many risks of property being claimed after purchase. Tread carefully if you intend on buying and I'd suggest renting a place for a couple months to determine if you are a good fit.