Okay, let's pretend that the hardfork is coming and I want to dump my S2X fairly quickly. Which exchange would be the best for me. I am from the US. Any help here would be greatly appreciated.
edit: oops meant to say B2X
It's unpredictable. Since there is no replay protection, each exchange will be employing their own dodgy internal replay protection to split the BTC they have in custody. Hopefully all goes smoothly for every exchange, but it should be assumed for any exchange that delays/complications could arise. The thing is, we have very little experience here. The exchange that performed best last time around (Bittrex) probably can't be expected to outdo everyone else again.
I would say if you are willing to keep your coins with a third party that your best bet at this time is Bitfinex. At least they have been very clear about how the fork will go down. Bittrex hasn't been forthright. Coinbase has promised full deposit/withdrawal/trading capabilities within a few days, but historically they are a bad exchange to use in these situations.