That's the hottest time of the year here in the south, so I wouldn't recommend that for you. Suggest you consider New England (esp. Vermont) or the California wine country. August might be too early for the fall foliage in New England, but September could be quite nice - check with tourism agencies about the best time for that. Lots of American history there.

The wine country is really nice, but can also be expensive depending on the type of accomodations you seek. Chain hotels in the nearby towns can be had for reasonable rates, but inns/B&Bs can be costly. If you're interested in that, get in touch with a poster by the name of Phoenix in the bicycling.com love forum. He lives in the area and can give you more details than I can. Tell him I sent you.