For Jerusalem it says that the population is estimated at about 70,000, of which 45,000 are Jews, 15,000 Christians (nearly half Syrians of the Greek Orthodox faith), and about 10,000 Moslems.
For Bethlehem it says the population is about 11,000, almost all Christians.
For Er-Ramleh, it has the population "exceeding 7,000, including 2500 Christians." It says the mosque in that town was built in 1318 in a style resembling the Romanesque transition buildings of the Crusaders.
There was a separate volume, Palestine and Syria, which I don't have, which would have given fuller information.
Remember also that Lebanon, although Arabic, was heavily Christian (mostly Catholic). Most left, starting in the early 1900s.