form.html.rb

<%= form_for([@project, @survey], :html => { :class => 'form' })do |f| %>
  <%= f.collection_select :survey_builder_id, SurveyBuilder.all, :id, :name, :include_blank => "Seleccione Plantilla"},class: 'select2'%>  
  <%= f.submit class: 'btn btn-success' %>
<% end %> 

routes.rb

      get 'surveys/show_questions', as: 'show_questions'

show_questions.js.erb

$('#temp_questions').html("<%= j render partial: 'question_builder', locals: {question: @question } %>");

survey.js

$(document).ready(function(){
    $(function() {
      return $(document).on('change', '#survey_survey_builder_id', function(evt) {
        var builder = $('#survey_survey_builder_id option:selected').val();

        if(builder == ''){
            $('#temp_questions').empty()
        } else {
          return $.ajax('show_questions', {
            type: 'GET',
            dataType: 'script',
            data: {
              survey_builder_id: builder
            },
            error: function(jqXHR, textStatus, errorThrown) {
              return console.log("AJAX Error: " + textStatus);
            },
            success: function(data, textStatus, jqXHR) {
              return console.log("Dynamic Survey Builder select OK!");
            }
          });
        }
      });
    });
  });

survey_controller.erb

class SurveysController < ApplicationController
  def show_questions
    @survey_builder = SurveyBuilder.find(params[:survey_builder_id])
    @questions = @survey_builder.question_builders
  end
end