Instead of driving an hour to the dealer, take 2 hours and put in a little
"elbow grease" and do it yourself:

Get the car really clean, then put 2 coats of "Rejex" polymer coating on the
car instead of any of those expensive "waxes".  Now when you wash the car,
dirt will virtually float off...because the Rejex is so incredibly "slick",
nothing really sticks to it.  You can even put it on the windshield, like
Rain-X...and it will make water bead up and reduce the need for windshield
wipers...especially at speed.  Oh...and the car will really have a
shine...especially with 2 or 3 coats.  Try it...you'll like it.

Think of this, 2 hours on a Sunday, good downtime with you and your car.
You save cash, you get a sense of achievement, and a cleaner car with
less scratches or left behind dirt.

It normally takes me more than two hour to do a full job, but.
Spray wheels with brake dust cleaner
Rinse car and wheels (leaves wheels basically clean for proper wash)
with hose and spray nozzle.
Shampoo with good quality car shampoo, not fairy liquid.
Rinse with the hose and lots more water.
Chamois dry.
Allow to dry properly in air.
Apply polish if dull and buff up (follow instructions).
apply wax allowing to cure before removing.
apply second coat of wax and cure and remove as before.
Use plastic trim cleaner to clean up any non body colour plastics.
Clean windows.
Redress tyres.

I normally do everything but not every time.
Everytime (once a month or about 1000 miles) wash and Chamois, and
windows.
every 3 months, Wax and plastic trim.
every 6 months, Polish and tyre dressing.
I'm lucky, in the UK we don't get much sun, even in the middle of summer
so 3 month waxing is easy to keep up.
Time varies between a couple of hours for the basics, to most of the day
for the lot.

Don't get me started on the interior.

Let's be serious:  If you go thru an automatic car wash, depending upon the
type of car wash, the possible problems are:

1.  The wheel guide scratches your alloy wheels
2.  In a "touchless" car wash, they use special chemicals to remove the
dirt, these are not good for special waxes, and some are known to discolor
windshields, and who knows what they'll do to the dyes in the soft top.
3.  Obviously, you wouldn't even want to take a Boxster thru a more
traditional auto car wash, as the weight of the "chamois brushes", etc could
play havoc with the soft top and will put a lot of pressure on the side
mirror mounts.

Gosh friends, I thought this was simply "common sense", but please feel free
to disregard this advice...I've only owned Porsches since 1971...what would
I know?