At least in American music, most love ballads are slow music of some sort -- rumba, bolero, NC2S are possible dances. Not necessarily slow like the slow dance you referred to in another thread. Lots of ballads are rumbas, which are a comparatively faster tempo.
I'm not sure how this plays out in other cultures -- for example, African highlife music, with which I'm very familiar, is uptempo for everything, from love songs to funeral dirges! :shock: