Jim,
One day? After eating and shopping, you're not going to have any time for
museums. Since you didn't say what you are interested in and didn't
specify where you will be staying, it's hard to make a recommendation. I
agree with all the other suggestions you have received, but . . .
if you are into decorative arts, the Franz Meyer on the Alameda cannot be
beat. It is near Bellas Artes (which has terrific murals, exhibits on
itself, and will have a temporary art exhibit or two as well)  If you are
driving (which I don't recommend), you can park under Bellas Artes.
Around (or close to) the Alameda you will also find a stamp museum, a
government folkart store, the old post office (not to be missed), and a
couple of other musems.
if you are into folkart and will be in Coyotepec (the Kahlo and Trotski),
be sure and stop at the Museum of Popular Culture a block off the main
plaza--ask at the Turismo office on the plaza.
If you want more detail, just give me a shout. Good luck.

Michaele and David Haynes    [log in to unmask]