The New York Times has a feature on Chicago's Latin dining scene in Travel this week.
Coobah, Rumba, The Winds Cafe, La Fonda Latino, and chain meat-orium Fogo de Chão are highlighted. Personally, I'm a fan of Lettuce Entertain You's Nacional 27, which while still part of a chain has the virtue of being part of a locally owned chain, something Fogo de Chão can't claim.
Worth a read. You'll need to register to read the article, but hey, it's free!
And make sure you check out the Valentine's Menu on the Coobah link above. It may be the most suggestive menu ever written.