Not sure about the rest of Bavaria, but "Helles" (Lager) is the mainstream beer in Munich. Weißbier (Hefeweizen) isn't that uncommon but rather cliche...
I don't know about Swabia and Franconia but if you are in Upper Bavaria (or probably any part of Altbayern [0]) and order a beer (without specifying anything else), you will definitely get a Helles.