Can I use an Ethernet to Wifi adapter on the 6500 Ethernet port to make it wireless?

Yes. Works as well as your wi-fi signal allows. You might consider a wif-fi extender with a built-in switch to connect your shack PC and Flex, That way, you have a solid connection for comparison, and can go wherever your wi-fi allows with the Maestro, laptop, tablet, etc.

I have had mixed luck with extenders and the type of network traffic the flex needs to pass. I would strongly recommend trying to use G (5ghz) not B (2.4Ghz) for your wireless link between your radio and your wireless router (less interference and greater bandwidth). It can work very well unless there is a great distance between your router and the radio. B goes further at lower speeds. I recommend you look for what is known as a "wireless bridge". Best Buy and others sell them, often thought of as WiFi adapters for game machines by the sales folks. These are usally a small stand alone box where you plug a network cable into your Flex and the other end into it. They can work great with the flex. K4QJZ