Which airline are you flying with? I got here about a week ago and brought my dog via Continental cargo. I don't want to freak you out, but you should be prepared for a frustrating and ridiculously unorganized process. I landed at around 9:15am, and wasn't allowed to get my dog out of her cage [even after a 10 hour flight] until almost 2pm, although I did get to see her and know she was alright. Here's what I did:
After passing through Customs and baggage claim, you go through security. The SENASA desk by the baggage claim is not for people who ship their pets in cargo, only go there if you pick up your pet with the baggage. You will probably do best to ask someone who works for your airline where to go next, because it may be different. I first had to go to a building by Terminal B called Aeropuertos Argentina 2000, to a small Continental office on the 3rd floor, and paid $110USD to get my dog's paperwork. Then, we went to the cargo area, which is out past Terminal A. You have to go through a security stop and give your ID, and then find your warehouse. Continental's cargo company is called Prodexco [or something similar] and it's the last warehouse on the right. Then the bullshitting really began, as we had to wait for the people from the cargo company to return, look at our papers, and send us to the SENASA warehouse, where they also looked at our papers and then told us to return to the airport to pay the SENASA fee at Banco La Nacion. After waiting in the same line as 20 other people trying to change currency, we paid $80USD, then took that receipt back to SENASA. Then they sent us back with everything to the original warehouse, who then said we needed another signature and to pay another fee at the tesoderia, a few buildings down. When we got there, the man looked at our papers and said he didn't know what to charge us because no amount had been written down. After several phone calls and the realization that my boyfriend was about to kill someone if they sent us anywhere else, they decided whatever the fee was wasn't that important and stamped our papers anyways. Finally, FINALLY, we got my poor pup out of her cage [15+ hours without a pee!] and she did her business the second we got to a patch of grass. What a shame that she didn't do it right in the middle of the warehouse, where the assholes in cargo had to clean it up!!
Once again, I'm telling you all this in the hopes that you will 1) have more luck getting through the process quickly than we did, and 2) so that you are prepared to be bullshitted and sent blindly all over the damn airport because nobody, not one person, knows what needs to be done to get a pet out of cargo. Bienvenidos a Argentina! It all worked out okay in the end, but I'd be lying if I said I kept my calm the whole time. If you need any other info, feel free to send me a PM.