Only the Princesses who picture is out front is guaranteed. If it is a crown then it could be any Princess. Unless Elena's picture is out there, no they are not guaranteeing she will be there.
My friend told me right now they are having trouble finding friends of Elena who not only look like her (in Disney's eyes), fits in the costume, is personable but are also fluent in Spanish. There have been some issues with having to use others and kids have walked up speaking Spanish, oops...... I wonder if this continues to be a problem if they wouldn't pull back on Elena to just the hours they can staff with a bi-lingual Elena.
