How else would you put it? This person has found an incredibly subtle way for asking something most people would be embarrassed to ask. Luckily, in Texas they have no shame (in a good way, that is), and they have no problem making such requests. Who can ignore this reasonable request when they ask so nicely? People are ought to keep the pool clean simply because the sign is so thoughtful.
Despite all the stereotypes, Texans are extremely genuine, friendly people, and it’s only if you annoy them that you might get to see their “bad” side we always hear of. It’s true they might have a short temper, but this is something anyone would get mad at, so can you really blame them?