Without a doubt, Soda Stereo. They aren't just my favorite Latin group, they might be in my top ten of all time. They're a solid 3 piece rock band with some very catchy tunes and a great front man. Sadly Gustavo Cerati passed away a couple of months ago, but if you're interested, I'd check out their album Cancion Animal or their Ultimo Concierto live discs. I also like early Shakira (I think the album is called Pies Descalzo) and Los Fabulosos Cadillacs.