El Santisimo is lovely - it moved fairly recently to a new location with rooftop dining - that would be the way to go as the inside space is nice but nothing spectacular.
Also recommend both cocina de socorro (fancier and has best seafood rice i had in all of colombia) and casa de socorro (more casual also good but not as good as the frou frou cocina de socorro. this nytimes article discusses both:
for a nice, cheap dinner without many other travelers, grab a pizza at pizza en el parque - you order at the walk up counter and then eat in the park with a stool as your table - very fun and lots of locals (at least i think they were local folks). its on the tiny parque fernandez madrid.
most excellent bakery (gold coated dulce de leche brownies) - La Milla. very fancy but worth it for an amazing sugar fix.