Here’s what Benny told Dean on their first meeting:
BENNY: I got something you need.
DEAN: Yeah, what’s that?
BENNY: A way out.
DEAN: *laughs* Even a dental apocalypse like you knows there’s no such thing.
BENNY: There is if you’re human. God has made it so. At least that’s the rumor.
And here’s the information we get in 8.02:
BENNY: Purgatory has an escape-hatch. But I got no idea if it’s angel-friendly.
Little bit more info in 8.05:
CASTIEL: The risk of crossing Purgatory with a Seraph… it’s less than strategic. And certainly when we have no reason to believe I can pass through the door that you’re headed for.
BENNY: You see, you’re an intact, living human being stuck in Purgatory’s craw. This dimension wants to spit you out, which is exactly what’s going to power our escape pod. Now, I’m pretty sure I can squeeze through, too, because, after all, you take away the fangs and the fun, I was born human, too, but…
CASTIEL: I don’t think it will work for me.
And the most recent (and intriguing) info from 8.07:
DEAN: What the hell is this escape-hatch supposed to look like?
CASTIEL: He doesn’t know.
DEAN: You just drug me through the fire. Please tell me you know.
BENNY: It’s here. They promised.
DEAN: Oh, ‘they’? Well, that’s comforting.
The difference between a rumor and a promise is… rather substantial (and, side note: I love how distinctive everyone’s dialogue is; I can hear Benny’s accent just from reading the rhythm of the text).
So, if the angels fed info to Benny, that actually brings together some other threads – like, for example, how Dean ran into one of the (likely few) 'monsters’ in Purgatory that had already gone on an established 'no human’ diet before he’d ever died (the angels picked out someone that would specifically appeal to Dean – and my guess would be that Benny is rather like Cas in S4; he knows enough information to accomplish his task but was not informed of the larger picture). We know that the situation up in Heaven is chaos – they don’t even appear to notice Samandriel is missing! – and yet they went to the effort of sending many angels to Purgatory to rescue Cas? Cas who did so much damage?
What do the angels know?
They know that Cas gave a big scary speech, killed a whole lot of angels, disappeared for months, finally reappeared in the company of the Winchesters, then went to Purgatory with one of said Winchesters. They might know that the other Winchester stopped hunting. They know that their prophet is missing – they may or may not realize that Crowley had him (it’s Cas’s info on what happened with Kevin that makes Naomi lose her smile). We also have no evidence, I think, of any angel except Castiel being able to currently track the Winchesters and it’s looking like he’s been able to do that because of his connection to Dean (going from what was said in 8.07).
The Winchesters have managed to upend all the plans that the angels have had; because of the Winchesters’ influence, Castiel turned on Heaven. I’m incredibly unsurprised that the angels want to keep an eye on them. And, sadly, very unsurprised that once they figured out a way to turn Cas into a sleeper agent, that they took it. Heaven’s inability to control Castiel has led to extremely wide-reaching effects that include the murder of many angels. They want to be able to control him and to control the Winchesters.
So, theory: I think that the angels have basically admitted to themselves that they don’t know how to solve the problem of Crowley/the tablet/etc. so they’re trying to see if the Winchesters will fix it for them. But, being angels, they are absolutely obsessed with trying to control everything, so they’re also trying to influence the outcome. The straight-forward approach didn’t work, so they’re trying to be subtle this time.
I also think that getting Dean and Castiel out of Purgatory separately was their ideal situation – divide and conquer. Whoever told Benny about the portal stressed to him that it was humans-only. He says multiple times that he doesn’t think it’ll work for Castiel. Why don’t the angels just yank Dean out the way that they do Castiel? Well, they know that Dean trusts angels about as much as he trusts any other supernatural creature, and whatever mojo they’re working on Cas is likely angel-specific.
Luckily, Dean is already suspicious of what’s going on, so that’s helpful. I’m hoping that he’ll have a reason to ask Benny in an upcoming episode who the 'they’ that told him about the portal are (though I suspect that Benny might not be aware that it’s angels – there are a number of different ways that I can think of that angels (or someone else) might get that information out into Purgatory).
…it’s been a while since I’ve watched a show that inspired me to brazenly speculate about future plot developments. I’m normally content these days to just watch and see what happens next. Speculation is fun, though. It’s always interesting to see how right and wrong I am.
Original Post: Angels told Benny about the portal?