It's usually "in" a town. "At" is for a point. You might say you were "at" a small town if you were talking about, e.g., driving along a route and that town was enough to say how far you had got, but that doesn't sound like your context.

We would say "in my hometown" or "in your hometown." However, the word "hometown" can also be used as an adjective. In this case one could say "At hometown parks..." This would refer to a park in someone's hometown. Since it is correct to say "at parks" in this instance the addition of "hometown" as an adjective does not change that. So it depends on the context.

At my hometown*