Not enough nice words I can say about Falafelito. I go there because it's near my work and I need a quick and tasty vegan lunch. The staff are lovely. They don't speak English (and why should they?) but are very accomodating if you are not a native Spanish speaker. The falalefels are lovely. The veggies are fresh and they respect the environment too. And if you're not full after their 'pacquete', they also have vegan muffins for sale.
There isn't a lot of seating space, I agree. Though you need to bear in mind this is the hub of cool and hip DF and it's one of the reasonable food options in the colonia. If there are no seats, you can ask for the 'para llevar' (take away) option and enjoy your tasty falafels in Parque de Mexico
Cons: Could open later! , I crave a vegan snack after drinks