You always want to look at the "Compra" column (buying pesos with dollars) and discount that somewhere between .05 and .20 centavos (depends on how much money you are changing and how good a client you are where you change as to what to expect).
Ambito currently shows a spread of 15.77 (compra) to 15.92 (venta) right now. Last night it was something like 15.88 to 16.05. My wife got 15.8 first thing this morning at our usual cueva. The price has gone down since last night/this morning a little, which is normal. The best days to change money, usually, are Tuesday, Wednesday and Thursday. Never change on a weekend or holiday if you can at all help it.
I used to use DolarBlue.net a couple of years ago, but these guys seem to have stopped posting updates both on FaceBook and their website. The FaceBook page is in conjunction with DolarBlue.net. Currently the FaceBook page shows an August price. 14.2 - 14.9. Same on their website apparently. Not sure what's going on with this. I stopped using DolarBlue because their spreads between buy and sell were ridiculously large and made no sense.
I switched to Ambito because it's so simple and I've never found them to be wrong. I used to say that about DolarBlue, so when I find that Ambito stops making sense I'll find something better.
InfoBae just shows one number that I saw. And the number they are showing is the "Venta" number that all of the other sites show. If you are going to use that number, take more off, like at least .25 centavos. InfoBae shows 15.92 and I'm betting that 15.65- 15.7 is what people are getting at the moment at most cuevas right now in the afternoon.
And BTW - you don't have to know well-to-do Argentinos to find someone to change money with. I have 2-3 working class stiffs who buy dollars from me all the time, for their savings. I sell at the average between the spread of "Compra" and "Venta" to make it even more of a win-win situation.