Not quite. You can only park at a resort if you are a guest of that resort, or if you are visiting that resort to eat or to shop (in the latter case, you have just three hours to park before you get towed).
This rule may or may not be enforced, depending on the season and the resort (high chance of it being enforced at monorail resorts during high season, low chance of it being enforced at value resorts at low season).