Yes, Challenges, regardless of if they are location-specific are visible to all customers in the Mariana Tek app.
For example, if the NYC studio sets up 10 classes in 30 days challenge for NYC only, the LA clients would also see that challenge is going on in their app.
The Challenge Locations field when creating a Challenge dictates which classes qualify for the Challenge. It does not dictate which locations can see it.
We recommend that you place the location in the title of each Challenge.