You failed to say what resolution you want to run on. I'll assume 1920x1080, since that's basically default for PC games now.
Judging by my system specs and the FPS range I get on 1920x1080 when compared to yours and the fact the game isn't very well optimized, I'd honestly say it'd be playable but not good. If you use the default low settings on 1920x1080 and get pass the initial 5FPS thing that lasts for roughly 10 seconds without crashing, I'm guessing you might get 20 or so FPS.

Again it's just a guess, but on low settings and not in incredibly demanding areas like huge cities, I'd guess you could get 25-30fps on that resolution.

Again it's just my guess though. Don't get mad at me if I'm way off.