Can I fight the 4 Ubers in single player or non-ladder battle.net?

The Pandemonium event can only be undertaken on the Ladder and Non-Ladder Battle.net realms and is not functional in single player or LAN games... without a mod.

Both the Pandemonium Event (Ubers) and Uber Diablo (Dclone) can be fought on the BattleNet Realms (ladder and non-ladder), but not on Single Player.