Falafel Considered one the popular dishes in Jordan, therefore there are many restaurants that are specialized in serving this kind of food.
To Make the answer Short, the best Falafel Sandwich in Jordan will be in Abu Jabara, one of the oldest restaurant in Jordan, Amman that started in refugee camp and then move outside to the more modern location.
Today you can find 3 locations for Abu Jabara in Amman, two of them (macaa street & al gardens) specialized in serving sandwiches and the main one in Al-Madinah Al-Munawwarah Street where you can enjoy dinning in and try different dishes of this authentic food.