If your time is limited, make sure that you go somewhere that has more
than one aircraft and instructor available. However, compare prices.
I like flight schools because of the redundant equipment and flexible
scheduling, but they can be pretty expensive (though maybe cheap to you
now with the U.S. dollar in the tank).

If you are going to use your skills in Europe, I think that it would be
important to develop your radio skills, so learning in a towered
environment would be good. I did my PPL training at a Class C airport
and have never had "mike fright" as a result.

Weather in the U.S. varies hugely, so avoid the north and Great Lakes
area in the winter, and avoid the south in the summer, Florida during
hurricane season. California probably has uniformly the best weather,
but inland CA can be extremely hot in summer and foggy in winter, and
the coastal areas can have days of marine fog. New Mexico/Arizona have
superb fall weather. On the other hand, learning how to make weather
no/go decisions is also an important skill...