Traveling in Colombia, you will usually find the arepa street vendors out on the street in the mornings and early afternoon, as the corn cakes are usually a breakfast or afternoon snack. Here in New York, the most famous of all Colombian arepa vendors is out only at night.
Arepas Pues Mixtas is in the business of arepas rellenas Colombianas, in which the corn cake is split in two to make a "carrier" and stuffed with the contents of your choice, ranging from chicken and beef to tuna, shrimp, and pork skin. You might as well go for the gold and get the arepa mixta ($8, below), a combination of everything.
I've never been a huge fan of indoor arepas. Caracas knows what they are doing, but lacks the right atmosphere that you find in Venezuela or Colombia when you share a street corner with others, trying not to get your clothes dirty as you eat the food you just got to watch prepared. Arepas Pues Mixtas is not changing my opinion on this, but does create a good product. The tuna could probably stand to be left out, but the rest of the meats are nice and juicy, and the pink mayonaise-based sauce is delicious. Use a fork for your first few bites or the whole thing is likely to fall apart in your hands from excessive weight.
83-15 37th Avenue, Queens NY