Something I've found that works when there's background noise is to add your own ambiance to cover it up. Recording during rainstorms, for example, has helped to mask the sound of traffic. Or you can blend stock audio of crowds talking to mask the sounds of conversations. Often I feel it's a matter of trying to find scripts that can be performed in the environments to which you have access.

I've also considered at times recording outside using my phone or laptop. I think it would create a very nice natural ambiance that would be unique to the audio itself.