I wish I could be more encouraging.

I've only been down to the Smithsonian (actually something like 16 museums, only most of which are on the Mall) once since 9/11. Security was different in different museums, some just looked at you and waved you through (no idea what they thought they were looking for), others hand-searched every purse and bag. I don't know if it's permanently different in different museums, or they stagger the searches, and I'm sure not going to ask. I didn't see any metal detectors or anyone being patted down that day, but neither would surprise me a bit.

You haven't specified what "minimally prepared" means to you, but I doubt if we're worried about a compass and matches here, and at the other extreme I doubt if you're planning to pack a gun, so let me just volunteer the information that carrying any pocketknife with a blade over 3 inches in DC is flat out illegal. They're serious. If they find such a knife on your person, you will be very lucky if the worst they do is confiscate it. In at least some government buildings the standing policy at the metal detectors was to call the police and have you arrested- and that was before 9/11. These days, I would guess that smaller knives would be confiscated, and later sold on eBay. The TSA gets away with this at the airports, so now they all think they should be doing it.

Quite frankly, the attitude expressed in your message troubles me. Not that you're wrong, I'm not saying that, but just that it won't work. Yes, they do think they have the right to paw through your pockets and pass judgement, and if you give them a hard time about it, they will give you a hard time about it, and they have vastly more potential in that direction than you do, with far fewer consequences.

IMHO, the best way to approach a visit to DC is to realize that you're going to a very troubled area under something approaching martial law. Think Belfast in the '70s, or Beirut. DC is one of the few areas in the country where the mere posession of a handgun is completely forbidden. Anyone daring to quote "shall not be infringed" is considered backward and ignorant at best, or subversive, possibly treasonous at worst, which means that in areas of the city gang members can shoot in the general direction of each other in the secure knowledge that no ordinary citizen can do a thing to stop them. This periodically earns DC the title "Murder Capital of the US" (greatest per-capita murder rate). Amazingly, most residents of the area think you're insane if you feel this is a failure of gun control. To them, it's obvious that it means that gun control must be expanded to neighboring states, then all states, then worldwide, because they always claim their problem is guns coming in from places where their laws aren't in force yet. Of course, they'll have that argument so long as there is any such place on earth.