Sorry my friend if your American you won't be able to open an account in Uruguay, that's for sure. Second, last time I went from Bs As to Colonia the guy in front of me was pulled over for having over the 10,000us limit on him. 10,000us is the total limit you can travel with these days anyplace in the world. WARNING besides the other problems you may have, they will confiscate any amount over 10k and fine you, DON'T do it.......................... they are always now checking boats and flights out of the country for this reason. If you really do want to risk the Uruguayan route,
then go by car over the bridge and be ready to bribe if caught and hope you can.
So what are your options, well first of all you are not a resident I guess, so you have at least 6-9 months to wait for permission to sell. ( it took me 10 months and then a 25k bribe ) you can buy stock in the stock market that's listed in New York and sell it there, a lot of Argentines do that.
Or find someone who can introduce you to some one to "move" the money for you, they will also collect it when you do your escritura. I can recommend someone for you, who moved a very large amount for me, but it took time. But take care, may be worth reading this
Argentines risking all to carry huge wads of cash - Yahoo! News
http://news.yahoo.com/s/ap/20100906/ap_on_bi_ge/lt_argentina_banking_attacks
GOOD LUCK