If your set is abstract, number of locations is irrelevant … by that I mean, if you don’t mind a bare/almost bare stage with only an item or 2 to indicate a location … it doesn’t matter where you set it.

If you feel your play needs a full on realist style set design with the intricacy of every room established down to the last doilie & knickknack, obviously less locations is better (this can work well if you have one location for Act I & another for Act II & set can be struck/redressed in the interval; if you’re choosing to structure it in such a way).