FXCM is no longer permitted to operate within the U.S., and does not accept U.S. clients. Furthermore, it's not possible for U.S. residents to access FXCM's TradingStation platform or MarketScope charts, even in demo.
As a U.S. resident your choices are pathetically scant, thanks to the CFTC (the Commodity Futures Nanny Commission). There now are only four U.S. forex brokers. And, unless you have a very large net worth and the ability to fund a very large trading account, only two of those brokers are effectively available to you: Forex.com (Gain Capital) and Oanda.
Look at both of them, and take your pick.
Your only other option is to move your trading offshore with one (or more) of the reliable foreign brokers we have researched and identified in The Offshore Broker thread.
However, if you are just starting out in forex trading, I strongly suggest that you begin with either Forex.com or Oanda, and forget about offshore for now. After you have proven to yourself that you can trade this market successfully (meaning consistently profitably, over the long-term), then you can consider taking on the added complexities of offshore trading.
Be aware that the Nanny regulator is tireless in its attempts to prosecute, fine, ban, and destroy offshore brokers who deal with U.S. resident clients. This adds a layer of risk to offshore trading which is not present in trading through U.S. brokers.