Cameras may have been allowed in Melbourne Sexpo but I don't believe you could easily take photos all over the place and of anything.
In the first year that I went, I brought my PowerShot G2 and took photos of the live action on stage. With the external flash firing away, it caught the attention of a security guard who told me that I couldn't shoot images or record video of the stage show.
I apologised and said I didn't know (I really didn't know it wasn't allowed). I quickly volunteered to leave the premises to save the rare images I shot, and the guard let me leave.
If you have been to Australia (Melbourne or any other city), you would know that Singapore is not very open. The western world, and almost all around the world, calls Singapore as "the nanny state". Don't expect too much from Singapore Sexpo.