Ben,
As the saying goes, "When in Rome...". Personally, I enjoy August in Seville (I'm from NM, not from Maine) because of the slower pace. People joke that during the early afternoon one can only see foreigners in the streets. There's a reason for this. Take advantage of the morning to see things, spend the afternoon lounging in a bar, go to a movie or go shopping in an air conditioned mall, and then see how the city comes alive during the early evening until late at night.
I have not actually visited either of the two parks, but neither is highly regarded by the natives. The are several public pools should you need them, and remember, a 45 minute car-ride will put you on the beach of Mazagón. Enjoy your stay.