SoCal

There have been several posts here, and on other sites (e.g., Cruise Critic, Lonely Planet) about the burdens of booking on Brazilian airline Web sites. There is the requirement for a CPF # (more like Social Security than citizenship; I am a permanent resident in Brazil and have a CPF), though some sites give the option to use a foreign passport number instead. Then there is the problem with some, not all sites, of using a foreign credit card. Some have reported being able to get around this by phoning the airline. Some have used local or foreign travel agents (though this can involve extra fees). I've booked TAM flights through Expedia; in one case I saved money over what I would have paid booking through TAM (plus was able to pay in US dollars, so avoided my credit card company's foreign currency transaction charge), but this is not always true, as you apparently found in your case with Kayak (especially true if there is a sale involved). Expedia currently shows a one-way GRU-GIG fare of $133 for 12/28 in the afternoon; $164 to SDU. TAM has international Web sites (plus offices in Miami and a toll free #). Some have reported being able to book Gol tickets easier by using the airline's Argentina Web site. You might also see if American Airlines can help (they're a code share partner of Gol).

Sales, at least on TAM and Gol, are often announced on weekends.

Yes, SDU, in downtown Rio, is a bit closer in than GIG, but if you're going to Ipanema/Copacabana, the difference is not huge, especially if you take the Real bus. You'd save some on taxi, but not enough, IMHO, to make it a big concern, given the total cost of your whole trip.

I would not book a flight anytime before 1 p.m. Once you land at GRU (and we are assuming you'll land on time, right?), you have to go through Immigration, then Customs (note: there's a duty free shop you can use just before Customs), then exit the secure area with your bags. There is a transit desk ahead of you and you MAY be able to use this if your second flight is already booked, but you may have to go upstairs to the check-in counter of your second airline. Then go through security and walk to your gate. The whole process may go very quickly, but since your flights are purchased separately, you may have problems if you miss the connection. Can't CO help book you on a connecting flight with TAM (they're both in the Star Alliance)?

If you want to save money, you could always take a bus from downtown SP to downtown Rio.