Jez — where are you coming from? That would give us a hint on what not to recommend — assuming you want to see something different from what you've got at home.Right off the top, Florida in August doesn't sound too cool — pun intended. Likely to be in the 90+F range for temperatures and about the same for humidity. Best run for some mountains, where it's cool and green, even in August.
The Rockies are spectacular any time of year, but their poor cousins to the east (the Appalachians) are cool, green and beautiful too.
As far as cities are concerned, it's a pick-'em kind of thing. Atlanta is beautiful and so is Charleston, S.C. Can't recommend much on the eastern seaboard between there and Philadelphia, but that's close to New York City and not far from there to Boston.
Most of the midwest cities have their charms, but you n eed to know where you're going and what you're looking for. Otherwise, you'll end up looking at a lot of steel mills and car factories which — unless you're a follower of Ayn Rand — are not things of beauty.
Anyway, before I ramble on too much, give us a little more info and we can give you a better idea of what might appeal to you. Knowing your musical preferences would also help a lot — especially if it's important to you.
cheers,
david