Well...just saying.
It's hard enough to get the Council to cough up when you destroy your car's wheel in a completely unavoidable pothole that's large enough to have it's own postcode - let alone trying to claim because of someone else's sign that you collided with whilst cycling like your arse was on fire; a sign that wasn't anywhere near completely blocking what looks to be a pavement that quite possibly you shouldn't be cycling down anyway........
It'll be a tough one to argue for sure - and I do feel for the OP, because pretty sure we've all done something similar at some point, and aside from pain and broken stuff, you feel like a bit of a dick.
As an aside, it's funny how society has changed over the years.
I came a cropper on my road bike when I was about 16, due to a load of small road coloured gravel/stones that had been put around the kerbside spilling out onto the road on a s-bend corner. I was belting it...as you do. Front wheel went from under me, I slid off the road and then got catapulted off the bike once the crossbar clouted a wooden post on the roadside (putting a nice dent and kink in my £600, so expensive at the time, bike). Meanwhile, my flight over the nettle ridden grassy bit resulted in a load of stings, but not as much stinging as when I landed on the other side...on the road again, and slid down the road on my side.
First thought was, fuck my bike's buggered - followed by "ouch". Went to the hospital, got cleaned up and went home feeling sorry for myself. There was no plan formed for trying to sue someone for gravel not being where it should have been, or not trimming the nettles, or having a wooden post at the edge of the road - and even if I had, realistically, it was mostly my fault for going to fast and not allowing me time to notice the bloody stones.