Cool! Yeah, I've never run into problems myself, but I've read plenty where cops have hassled cachers and a couple places where they've sent in the bomb squad to blow up a cache that was improperly marked, afraid it was an IED or something bad like that.
As for me, I actually will be in La Hulpe for a week for a work conference. I won't have much time outside of work to do anything other than drink and hang out, but the weekend before I'm planning on spending Saturday and most of Sunday in Bruges (I fly in at 0800) and the following weekend, I've got Friday evening and all of Saturday in Brussels with a friend of mine from Switzerland before flying back out on Sunday morning.
Unfortunately, no car for me... I like the idea, but this time around, I'm going to avail myself of the wonders of European mass transit. I understand it's far superior to most public transit systems in the US (meaning most European public transit, don't want to sound like I think "Europe" is a single country or anything)... So trains and busses for me.
Next time, if I have vacation time to tack on to the business trip, I may rent a car instead so I can visit a few different countries, but that's in the future so who knows what will really happen.