Potty training and shared toilets..help?

My 2 1/2 year old daughter is fully potty trained...that is at home. She refuses to use a toilet that is shared...in public restrooms, "preschool", etc. She can't explain why, she just doesn't want to use them. She would rather pee on the floor, so we need to keep her in pullups for school. Any suggestions? Oh..and at stores the problem isn't so much the sharing, but the loud flushes from the water conserving toilets..they scare her and make her cry.