I've recently moved here and have been changing my dollars at a cueva in Recoleta. The average rate has been around 50-60 centavos below the rate posted by Dólar Blue on Twitter, which would correspond to the "venta"-rate on ambito.com. Now, this seems to be a pretty bad deal, if 10-20 centavos below the "compra"-rate is what you can expect. The place seems safe and it has been without hassle so far, and I don't really want to pick randomly in Florida, but could I expect a better rate elsewhere, and in that case, could someone recommend a safe place via PM?
You are looking in the wrong column on Ambito, to begin with. "Venta" refers to selling Pesos to buy Dollars, not the other way around (and you'll never get anywhere near that actual price if you want to buy dollars with pesos - the spread on this side is indeed more than 10 or 20 centavos no matter what the published rate says). You need to look at the "Compra" column, which is buying Pesos with Dollars and go
down from there.
Of course, that's only 15 centavos or so off your 50-60 centavo difference (as I look right now), and that's still not great. You're really looking at .35-.45, instead of .10-.20 (which has been my experience), so still about 25 centavos less than you should be seeing.
BTW - .20 - .30 may be reasonable for smaller amounts of money (and certainly for 20 Dollar bills - most places take a bigger discount for anything smaller than 50s). I usually never change less than $1000 USD. The times that I do and still get around .20 difference (instead of my usual .10) may indeed be because I'm a repeat customer at my favorite arbolito (cuevas are the bigger guys that mostly work behind the scenes and even do international transfers - the arbolitos are the guys who do the actual changing to the general public, for the most part).
As Ben mentioned, it's all about not accepting the first offer, or maybe even the most convenient place (convenience? Hah, after all, this Argentina. I don't think there is a translation for the word in "Castellano"
). You don't have to have "special deals" with anyone to get decent rates. I've been changing money here for a long time, true, but I submit that it is my experience of knowing how to deal with them (and when to stop dealing with them), not necessarily that I have any kind of special deals set up, for the most part. Indeed, it has been my experience that the longer you do business with someone here, the more likely they are to start trying to take advantage of you over time. Not always the case, but I have been royally surprised a number of times when dealing with some long-term relationships.
And depending on where you go in Recoleta, you could have a hard time getting a good price because everyone knows a lot of tourists stay there. Although, I do know two places (one very good, and one so-so) that have been reasonably consistent over the last 5 years I've lived in the area.
It's a matter of staying in touch with the prices and not accepting crap from aprovechadores.