Hi, I can answer this as someone that has lived in a muslim country, and who has been married to a muslim man.
During Ramadan sex is not allowed during daylight hours, even between husband and wife. However sex is permitted after sunset, between husband and wife only.
Ramadan is a time of being good - even if someone is not a good muslim, or as good as they should be the rest of the time, during Ramadan all muslims try to be the best and most holy that they can be for this one month of the year. Sex outside marriage is not permitted in Islaam, therefore muslim men will not visit prostitutes even after dark during this time. (You will have the occasional muslim man that will visit a girl after sunset; that is down to their own conscience and their own interpretation of the Koran. It is for them to make their peace with Allah for doing this)
Eid marks the end of Ramadan and is a day of celebration. This is the day all the punting muslim men will want to visit ladies again (whether in the day or night!) so make sure you have plenty of space in your calendar!!
Hope that helps
Hadley x x