I deal with this issue ALL the time. (privacy in public places) I work 12
hour nights 70 miles from home and "camp over" between shifts. I'd offer
this from my experience with daycamping/sleeping:
Curtains work great for keeping the general public from seeing in the bus.
They keep the sun out so you can sleep and stay cool.
HOWEVER, full curtains all the way around the bus have an uncanny way of
attracting the local constabulary. They can't resist hassling the occupant
of a fully curtained bus as they figure you for a homeless guy. This is true
even with the top unpopped and no other outward signs of permanence or
troublemaking.
The answer seems to be to
    1. park strategically-use vegetation or structures/walls to your
advantage so you can:
    2. LEAVE curtains open!  Close only the back and rear sides perhaps.
Looks like you are concealing shopping bags, etc. I block the left jalousie
view with a duffel bag and hang a jacket on the poptop knob to obstruct the
view from the front windshield.

I have unscientifically proven (over sevaral years/tons of camping)this to
be superior to full curtains at keeping the inside of your van private. Draw
less attention-don't make it a game for everyone to see if they can spot you
thru a crack in the curtains.   Also I can't wait to try out the 84 westy I
just got running as it has dark tint all around, even the windshield except
for a band in the middle a foot or so high.  It is hard to see in unless you
try, so I figure that NO curtains will be pulled in this one. My experience
to date has been in my '77 in urban Indianapolis. YMMV.
One more thing: don't forget the coffee can to piss in. It draws attention
when you hop out and take a leak behind a door or something. Good luck and
be safe. Use good judgement when picking a spot. Hope this helps.
Jay Schmidt
Seymour, IN (and Indy half of every week)