var strNewString = $('#FIELDID').html().replace(/\Select taxonomy/g,'NEW TEXT');
Replace the #FIELDID with the field id this is in #acf-field_#####
Replace the NEW TEXT with the text you want to show
I have a custom scrip page but you could add it inside script tags on the page that is loading the form.
I hope this helps someone as I was searching all the wrong places for this.
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