Hi jrdelar,
If you're planning on being here for the first two weeks of August, you should have better luck than if you were planning on the last two weeks, but you'll still probably find quite a few shops and restaurants that are closed for vacation. At least in Barcelona, more people tend to close during the latter part of the month.
Since most of the locals are on holiday, the percentage of tourists naturally goes up; so while the residential areas might be pretty deserted, many of the tourist-oriented sites and businesses are still open. If there's anywhere specific you want to go, though, I'd make sure you check ahead of time to find out exactly when they'll be closed.
Hope this helps,
Greg