I'm afraid I don't know the exact answer, but this locality of Morava and Dyje junction is full of turists, especially during weekends. So every potencial police officer should understand what "turist" means
The only problem could be the status of this land - it's illegal to camp in national nature parks and reservations (in czech "Prirodni Park" or "Prirodni Rezervace"). I hope somebody in the forum will be able to tell you more.
And BTW: The best way to visit these caches is to bring your own bike or to rent one in Breclav. The land is completelly flat and when you're walking you're not fast enough to run off mosquitos