Just a few ideas of a couple of things to try when there are few people around:
1. Take urban landscapes using a normal to moderately wide lens and look past the person. Then when you take the photo, it’s an urban landscape with people in it.
2. If they notice you, the urban landscapes motif can be a conversation starter, after which you can ask to take their photo.
3. Don’t stalk or walk towards a person with an intention to take their photo. Instead have a subject which lies in their path. They will come to you and then you can incorporate them into your “urban landscape”.