Gilead--no single women (rare exception) because it is designed to train male WTS administrators.
When I was young, I wanted to be a missionary. I think the idea of living in another country, learning another language, and experiencing another culture really appealed to me. But I was told that the Society no longer allowed single sisters to go to other countries for safety reasons.
Given the fact that I was young and had not yet formulated my own opinions, I bought that lock, stock, and barrel. Now as an adult, away from the sexist, repressive regulations of the borg, I've lived in another country, learned another language, and experienced another culture. And I've done it all while being single. Hooray for me!