Are you sure about this? If there is only one Mind, then is it not reasonable to conclude that that Mind is your own? You can never know (through the use of your physical senses) whether anyone else is even conscious, can you? You can never know if they are not just figments of your imagination. However, you can know, from personal experience, that you are conscious, so what makes you think yours is not the Mind that creates all reality?
It is possible to conclude that someone/something is conscious. Quite simply, observing a living thing, you could take into account the properties of consciousness (which include awareness of oneself and surroundings) and arrive at a conclusion. It may sound simplistic, but I find it fairly tenable.
Also, if your perceptions of reality are not real, then what is the purpose of your existence? And how do you know your physical body is real?