As for where they can spawn....I have seen them in every cave around Vallaki at one time or another, from Zeklos to Midway, except for the Hobgoblin cave and the wolf cave to the East of the Elf enclave. Those are the ONLY exceptions that actually come to mind. In every other cave, its literally been, at one point, walk in, see oozes/puddings, walk back out. Seriously. Obviously they don't spawn in the actual dungeons themselves (Zeklos, Crypts, Ruined Monestary, etc.), but every place where the spawn can be random seems to generate them.
And as for how to deal with them...Well, as was mentioned, running is usually the best option if you don't have a monk. One buffed monk, however, runs through them like a hot knife through butter. My L10 wizard buffed a L10 monk and just stood back, watching her kill WELL over 100 Large and Medium Ochre Jellies in a particular location one dungeon run. I literally got bored watching her carnage and would throw in an occaional Magic Missile, Flame Arrow, or Firebrand just to liven things up on my end.
So, it seems puddings/oozes literally are Paper, monks are Scissors, and the rest of us are just Rocks.