Can you provide a picture ?
What are they planted in ?

Did you fertilize your plants?

I will provide a picture. They are planted in a border bed, more or less an amended topsoil. I fertilized with 10-10-10 type pellets in mid June.

I am in an urban setting and sunlight can be dappled. When we moved in, tomatoes in that same spot grew pretty well, but the fact is they are only getting about 6-7 hours of direct sunlight a day. I'm wondering if that has something to do with it.

6 hours of direct sun is considered "full sun." Tomatoes would be happy with that. For instance, for many years I grew tomatoes right up against the east wall of a house: no sun after noon. They did fine.

That amount of dappled sun might be a problem.

How's the weather been? Hot and/or humid conditions can
prevent fruiting.

I'm in SoCal and I get fruit early in the summer and then
the heat hits and I get very little fruit set until it
cools down some.

Really hot weather (highs above 90-95, overnight lows above 75) prevents tomato pollination/fruitset. Really high humidity can do the same. However, there should still have been flowers.

the more i watch the spot, the more i think it is a simple lack of sun. i live in a sort of complicated urban sun environment, with part sun/ shade and full sun/shade all mixed together. i think two of my shrubs are starting to shade out the tomatoes after noon, plus the sycamore above seems to have filled out substantially this year, blocking almost all sun before noon. it is kind of hard to tell because i'm at work all day so today (saturday) i'm going to see when they start getting sun.