Don´t forget that you are in a Muslim country, that is to say, every Friday at 12:00 (half a day) all the trades, restaurants, museums, etc. close the doors. It is the time for the most important prayer of the week and the day of rest that the Coran dictates
Of Turkish influence, there are numerous steam baths with natural hot springs in the city. The price ranges between 500-100 YR (2-3 Euros) and many of them are opened beyond the midnight.
It is a good opportunity to relax and to be shared little time with yemenis people. They work different days and hours, for women and men. Better to ask before for avoid surprises.Hammam at-Tawashi or hammam al-Maydan are some of the best opcion in the old city.
Exchange shops are in the streets of the new city or around Bad Al-Yemen door, in the ancient city, so, if you have cash, don't need to waste your time in going to the bank.They offer the same rate, but you shut to ask before in a couple of places for be sure about the rate before change your money. the prefered currency is the US dolar, but you dont have any problem for change euros too. At the airport, you can change also a little money, for pay the taxi and have little cash in your pocket.
If you want to understand better the culture and the Yemeni mentality, you must know something about Qat (Catha Edulis). It is a legal drug in Yemen, which has a stimulant effect. It is an important part in the economy of the country . After lunch time, the country slows down, and the Yemenis re-join to chewing Qat, doing of it a forms of social relation. Any corner can be an unexpected market. Up to you to accept an invitation!!!
If you come to Sana'a in the rainy season, do not forget to stop in some of the footbridges that there crosses this riverbed of torrential waters, beside to the old city. When it does not take water it is an important route of traffic of cars to cross this part of the city of north to the south. If it rains, the route remains interrupted to the traffic a few hours, until the water disappears.