I'd say go for the 5d2. Pick one up new or lightly used and you'll love the quality. Sure, the AF system is pretty bad, but if you're shooting in decent lighting out on the street (or maybe even not so decent lighting) it'll still be pretty great. You have a nice set of lenses currently, and know what you want to get next. The 24mm will seem new to you, it's going to be a lot wider than you are used to, but it's great
If you're really concerned about cost, go for the 5Dc. I haven't owned one, but everything I've heard about it says it's still a great camera. What about renting one for a weekend when you plan on shooting a bunch of different stuff? It'll prolly cost you $100-200, but it'll really help you make up your mind. LensRentals.com has a 5d2 for ~$140 with shipping for 5 days rental.
That's what I forgot to mention! I ruled out the 5Dc, because I would miss Magic Lantern, it's very handy...
The thing about the 5DII is, if I go full frame, why not spend 2000$ more for the 5DIII? It would last a lot of years anyway...
One more thing is holding me back, the (for me) unfortunate timed rumors about an entry full frame, although I start to disbelieve them...
And yes, I can't wait to shoot the 24mm full frame!! Renting is as well a good idea, I could borrow a 5DIII from a friend, when he isn't using it, what's rare, but possible.
Do you believe that the 5d2 might hold you back significantly? Owning both, I honestly can say that the AF system is the single biggest improvement, although there are lots of small tweaks that are nice, and I believe the ISO Noise is nicer and less than the 5d2. However, you would also be missing out on ML, at least for a while. That and it's also $2K, which you might be better served spending on a lens or two.
As for the 135L? Awesome lens, I love it. Probably the only lens I would love more is the 200L f/2, but that's not gonna happen anytime soon for me. You should get it no matter what.
You may be right about the not to big difference of them two cameras, especially for a full frame novice, who's job doesn't depend on critical moments which are not to be missed.
As for the 135L, no question it's an awesome lens, everyone praises it! I had the opportunity to try it two times and I like it so far, only that the focal length is very similar to my 100L, so the 135L still can wait for me some bit more. I may even trade the 100L for the 135L, have thought about that as well .