1
If it is a big amount it is better to do it in Amman but not at airport in town you get better rate.cheers
2
Yes, forget the airports, go instead to one of the money changer's offices in downtown Amman. Use an online currency converter to establish the approximate value. In Amman, you may need to shop around. Many currency exchange offices will try to cheat you. One where I have always been given honest rates is a shop on the main street (house no. 16) in downtown, on the same side as the Arab Bank building and quite close to it. The business is recognizable by having a grey, futuristic-looking, metal bench in its (tiny) lobby opposite the counters.
