The above comment is incorrect, even for systems without integrated dehumidifiers. AC systems absolutely do have a higher load with higher humidity because ambient water will condense on the evaporator coils if the dewpoint is higher than the evaporator temperature (which it typically is).
That said, it still may be more efficient to open your windows, depending on the humidity.
I stand corrected. Apparently 60% humidity or so is the line. That said, I live in Florida and haven't ever had an issue, but maybe that's because the A/C runs so much anyway...
That said, it still may be more efficient to open your windows, depending on the humidity.