I've done Spanglish before and if it were speed dating, I would have tag-teamed a non-native Spanish speaker who was serving as the Spanish expert along with a non-native English speaker who was serving as the English expert.
Then I would have had a quickie with an early 20-something guy who is from Misiones (maybe) who is in Buenos Aires studying fashion design.
Then there would have been consecutive ladies in their 60s from the Buenos Aires area (one of whom I'd have to have shared with a married guy from Montana) and finally a really cute mid 20-something Argentine that I would have had to share with an American girl.
You might find this hard to believe, but I didn't sleep with any of them. I didn't even kiss any of them... or get a phone number, or ask for a phone number, or get asked for a phone number.
It is set up like speed dating in that you talk to someone for a short time and then move on. If this were how religious conversions were done, then it would be compared to religious conversions. It is how some job interviews are done, but comparing something to that isn't a great way to get people to come out and practice their Spanish... or English.
Most people are there to practice their Spanish/ English.
Some people might want to see if they can make friends to practice outside of Spanglish.
Some people might be interested in meeting someone to date.
And some people are interested in the cultural exchange aspect and learning about the world of someone from a different background than their own.
The two older women that I spoke with were obviously interested in people from different parts of the world and the lives they left behind. Since the crash, the locals can't travel nearly as much (some haven't left the country since), so they like to interact with extranjeros in an attempt at filling the void from lack of travel.
Go, enjoy it. It's about AR$20 and lasts about an hour and a half. If you need to be talked into it just so you can do something that's going to improve your Spanish, it might be too much for you. Hell, TRAVELING might be too much for you. And when nobody hits on you, don't come crying back to this board saying "I was hoping that it would be a little more like speed dating than it was... :-( "