It's no accident that Sonnet 75 begins with a reference to "my thoughts": this poem basically takes place inside its speaker's head. Thus, in a certain sense, the poem doesn't have a setting, because the speaker never tells you that he is standing in a particular place, or living at a particular time. True, we do know that he is in a relationship with someone (the "you" that the poem addresses at several different points), but it doesn't sound like he is physically in the same room as that person. After all, if they were in the same room, they would probably be talking to each other, instead of communicating through poems (or those funny thought bubbles that you see in cartoons), don't you think? (We'd like to think so, at least.)
Still, the speaker's mental journey does take us to a few distinct locations. First, we hear about food, which may make us picture someone eating, indoors or out. Next we get a clear outdoor scene, when the speaker tells us about rain falling on the ground. What about the miser imagery in lines 3-8? Well, since the miser's whole debate with himself is whether he should stay holed up with his wealth or show it to the world, we're going to say that these scenes take place indoors.
The gluttony idea is harder to place. One could imagine gluttony as taking place in a big banquet hall, or it could be a matter of eating in secret, alone. Either way, it definitely seems like Shakespeare's speaker is most interested in what these figures (miser, glutton) are doing, not where they're doing it.