There is a chain of hotels, Fragrance Ruby, Crystal, etc that are right in the center of Geylang, all girl-friendly. Also Hotel 81 and several others. You can book the Fragrance hotels right at the airport for S$28. I just got back from SP tonite. Also did some mongering in Batam, Indonesia. You can take the ferry from Harbour Front for S$24 RT. Johor, Malaysia (40 min taxi ride) is pretty good for whoring as well.
Good luck and enjoy. There are literally 100's of girls to choose from