You have to get clever when searching CL. Plenty of places that allow cats don't click the "Cats OK" box. Instead of using that search filter, include the terms -"no cats" -"no pets". In your case, -"no couples". My CL searches to filter the fake 1BRs get pretty crazy (-roommate -"room for rent" -jr -junior -studio, etc...) but their search engine handles complex queries well.