I would not buy bitcoins in any way that requires me to show a legitimate ID or otherwise seriously compromise my anonymity. Bitcoins are roughly as anonymous as the method used to obtain them, just keep that in mind at all times. The cash out is about as anonymous as the method used to cash them out. Mixes are really good for making it so the feds can't follow the money back to a vendor, but they will make you susceptible to money laundering charges, so my advice is to mix bitcoins and cash in and out in ways that don't require legitimate identification.