Hey,
To answer the original question.
Argentine girls of your age have to get settled. Their biological clock is ticking. Therefore, they only target local men who will support them financially.
Unless you have a business link to the country, you, being a tourist, are of no interest to these girls. Whereas female tourists have all it takes to have a fling abroad (they're not staying), male tourists don't (they're not staying). That's life. Only independent women from emancipated countries like Germany, Holland, Sweden, the UK etc. can afford to have a short-term relationship with a foreigner, it seems.
Please, don't let the idea of not having a girlfriend ruin your stay. Argentina has so much to offer. Explore the interior, cross the river and visit Montevideo, take up Spanish and read tons of Latin American literature, indulge yourself in the truly fascinating history of the continent, do volunteers work (you'll be amazed about what you'll learn about yourself)...
Don't waist your time and energy on women, don't let them sour your stay. And if you feel really lonely, I am afraid that, at my age, I agree with "hannstew": Buenos Aires is stacked with beautiful girls who trade their looks for pesos. Sad but true: women treat man like ATMs. Well... don't let them down!
I have learnt this the hard way during a one-year stay in Rome, a place where couples from all over the world feel the urge to declare their love in public, all the time. (By the way, Italy is a country quite similar to Argentina, sharing the same, almost pathological, obsession with female beauty.) Having learnt my lesson, I went to Argentine and I had the time of my life.
This might sound like a paradox but if you do want to end up with an Argentine girl, than go back home. At home, YOU will be the local. You will have what they need (i.e. financial means, own place,...). You'll see, it will be a piece of cake!
Face it: you can't beat the laws of biology nor thousands of years of evolution.
Good luck!