I used OpenTable to get a reservation, after tring 4 or 5 places (for 1!). Grillao was terrific! Delicious salad, perfectly cooked Angus steak, incredible dessert, and a fine house red wine. Grillao has a simple menú. People seemed to be enjoying their meals! The decor is great. The only challenge in "ambience" is that it is LOUD. The servers had a hard time hearing me, I couldn't hear them. Acoustics are not great, lots of people talking. But, I would definitely return!
I had dinner at El Jardin, it was amazing, it's nice and cosy and right in the middle of Colon.
I 100% recommend the cheese fritters and the oysters, one of my favourite things to eat in Madrid: