We are here not in the MS Excel forum.
But when you create a PDF with Save as Adobe PDF you have to select PDF/X-1a to get a CMYK file.
But be aware that Excel is only working in RGB and even if the output might be converted into a CMYK file, it will not mean that this file is print ready. Probably the black will consist of all four color plates.
Don’t use the virtual PDF printer. What for? From professional applications like InDesign, you can export a PDF, from MS Office you can save as Adobe PDF. Even if no Acrobat Pro is installed you can Save as PDF from any print dialog, even if this PDF is created with Apples Quartz technology.