After spending one day there for trading places, I would not recommend bringing heels to CSS. Dealing with the stairs is one thing, but some of the walkways down near the beach also had grates running on top...don't think they'd be very heels-friendly.
We were in block 3, with a flight of steps down to Pallazina and the beach and another up to the Balloon Bar and Cassanova and I wore heels in the evening to go to dinner. There are hand rails to use if it's slippery after rain. The stairs at CSS really weren't a problem and we had a wonderful Christmas there!
My first trip I only brought and wore flat sandals because of the reviews of uneven stairs. My second trip I wore heels for the evening dinners, except on the Starlight Gala (which is on grass) and beach party nights. If you wear heels, and are somewhat accident prone, you should be extremely careful walking around the resort...walk slowly to not twist an ankle, especially after having a few libations!
My wife wore heels ( always does spike heels) every night, if we wanted to go up to main lobby or Casanova restaurant, or the bar up top we just called for the van to pick us up and drive us up, after the evening and time to head back to our room she took them off and walked back barefoot!!
If we spent the evening down below at Palazzina or Bella Vista she wore them all night, on the nights of the beach gala and the international nights at the beach or on the lawn we both were barefoot as we had room in Bldg A.
Actually she had more trouble with the wooden deck area at CN because of the spaces between the planks!!!
Heels can work if you just plan ahead My wife has a large collection and was not leaving them home and she did fine.
In the evenings, I always wore my heels!
However, I always made sure I was holding Hubby's hand when we were on the stairs, or when the slope of the walkway was uneven!
I did make sure I had more manageable flats on the Galas (in the grassy areas) and Beach BBQ evenings!