Basically this rests on what you think delineates something from existing or not existing. Physics has absolutely nothing to say on this -- something exists only if it's observed, yes, but 'obervation' can come from a photon or electron or something.
So, there are two basic ways you can go about this: you can say that what exists really exists, and we're just seeing it. This is entirely consistent whith Physics, because as things in the universe of course we can interact with other things and thus observe them. The other way(which I think you're going for) is to claim that there is no independent reality of what we as beings perceive. The biggest problem I have with that is, of something exists to perceive things into existence, how does that thing exist? What perceives it? Is it possible for something to spontaneously come into existence by just perceving itself?
All these questions and more make the perception-based view of existence much less teneble than the reality-based one(that is, the universe exists because it exists).