temp import permit to uruguay
Every time i've entered Uruguay (last was 2011) they have given me a 12 month temporary entry permit. depending on where you exit - they might not even ask to see the document - ie. when I've thaken the buquebus ferry (http://www.buquebus.com/
) accross the river to Buenos Aires I was not asked to surrender documents prior to boarding the boat. When I got to the other side I did the normal temp import into Argentina.
Same when I travelled north into Brazil via Rio Branco - I was not required to "leave" Uruguay before entering Brazil - in fact the customs/aduana is several miles inside brazil and they did not do immigration there - I had to ride to the next town and find the police station where I got my passport stamped.
If you enter Argentina at one of the consolidated borders (the river crossing at Fray Bentos) the Immigration/Customs offices are shared by both countries and frequently the documents are simply passed from one officer to the other behind the counter.