Out of line-of-sight, whatever the inconvenience, is my advice.
As for hitting anything in the floor - building codes specific that pipe and electrical in walls or floors be set back from the surface. Unless you are using an very long drill bit, or ram it all the way in, you should have no trouble at all. Take a look at the floorplan layout, you out to be able to determine the likely plumbing runs as the stuff is almost always run least-distance, with adjoining bathrooms set with their plumbing fixtures set back-to-back to share a common thicker wall to accomodate the plumbing.
And just to minimize the hazard, use a small drill bit at first, and watch what kind of debris you are getting with it - you start seeing putty colored plastic or metal shavings, you know you've got a problem.
My own is mounted across the side/end of a closet, with a large 2-suiter and other goods hanging in front of it. A 'smash and grab' isn't even going to see it. And I deliberately faced it so the opening is to the rear, making any sort of pry-bar action much more difficult. It's lag-bolted into a stud and the slab.
I think I've made it as secure as a sheetmetal cabinet can be.