I can't deny having dreamt of the same thing in my youth. Hell, the thought still crops up in the back of my skull from time to time. But I'd have to agree with Malte on one thing: If there were dinosaurs around, they would likely have been discovered by now due to the sphistication and sheer resolution of some of those satelites in orbit.
Granted, there are still areas that are unexplored, covered by thick jungles that would obscure visibility from space, but the bigger dinosaurs would not be able to hide in vegetation this thick. Although I disagree with you on one point, Malte.
There were plenty of dinosaurs who were small enough to hide in such environments. Compsognathus, Coelophysis, Leallynosaura, Micropachycephalosaurus...possibly even one up to the size of a Minmi. The towering hulking lumbering giants of the Age of Dinosaurs were actually a minority...