Use promiscuous to describe someone who will say "yes" to just about anything. If you are the kind of person who will go on a date with just about anyone, you might get labeled promiscuous by your peers.
Promiscuous is not limited to a romantic context. Long ago promiscuous described "a disorderly mixture of people and things," and shades of that original meaning linger. If a chef at an Italian restaurant is promiscuous, you might find him mixing ingredients from South America or Asia into his pasta. Carpet bombing as opposed to targeted invasion might be called a promiscuous use of military force.