Mark's (salvador&armenia) Caesar is pretty much perfect the only reason I'm still surviving this town (okay and maybe the fact that Starbucks now carries the lemon loaf... Now all I need is for them to bring Peppermint Mocha to argieland). They do sometimes go overboard with the anchovies, but overall it's consistent in quality. Kansas' caesar reminds me of what you would probably get at Pizza Hut stateside, but they do offer the only Mediterranean with real feta cheese in town (or, at least it's the only one I've found). The serving size there is a plus. Their raspberry vinaigrette is on spot and they do also sell the dressing in a jar if you wish to take some home. Centro cultural Plaza Castelli (Conde&Echeverria in Belgrano R, kind of a hidden gem- the patio in the back is totally worth the trek from Palermo) has a variety of salads for lunch and you can sit outside on comfortable chairs and a decent amount of shade and greenery. They do offer a pretty good caesar, with some kind of rotisserie chicken that basically melts in your mouth. Not by-the-book caesar but hmm.. I'm getting hungry.
Dressings: You can get some pretty decent ones (organic, original mixes) at the Carrefour on Elcano and Enrique Martinez. Way in the back, near the spices and olive oil. They have everything from 1000 island to a few kinds of bbq. But that was last month... You know you never really know here.
I miss NYAJ's Waldorf... You really can't get here.