If an effect states that a creature or land enters the battlefield tapped unless a condition is met, Thalia’s last ability has it enter tapped even if that condition is true. For example, your opponent may reveal a Plains while playing Port Town (from the Shadows over Innistrad set), but Port Town will still enter tapped.

If Thalia enters the battlefield at the same time as an opponent’s creatures or nonbasic lands, those creatures and lands aren’t affected by Thalia’s last ability.