I like the food at Coca a lot, and I've never had a problem getting seated(Even on a Sunday), however if I was going on a peak hour I would definitely call ahead. I love that they take your cell phone number and call you when a table is ready - take your time and walk around Lawrenceville instead of hanging around outside waiting.
My biggest complaint though is that the service can be slow sometimes. I've been in there a few times where it has taken longer to be greeted than to get a seat.
They have a small patio if the weather suits.