That could be true, but I remember in one of the early episodes (actually I think it's the beginning of All Shook Up) Lois ordered a Cafe Mocha from a street vendor, and Clark ordered a Cafe Latte.
Lois did not request hers as decaf. She requested it with nonfat cream, no sugar, extra chocolate (I think, it's been awhile since I saw that episode) and Clark requested his with extra cream and three sugars. Something like that.
I think if it was implied she drank decaf, that she would have requested it then.