Form Design issue - How to handle a parent association input..

I have an Event Model with a parent Place association

class Event < ActiveRecord::Base
  belongs_to :place
  accepts_nested_attributes_for :place
  attr_accessible :place_attributes

In a new event registration form, the user should have the choice to :
- select from an existing Place
- enter a new Place in a nested form

= simple_form_for @event
    = f.association :place, :collection => Place.all(:order =>
'label'), :prompt => "Choose an Place", :label => false
..
   = f.simple_fields_for :place do |pf|
           #geolocation.form-inputs
                  = pf.simple_fields_for :geolocation do |g|
                      = render "backoffice/places/
geolocation_fields", :f => g

should I manage that with a jQuery script ?
- when user select a place , it will clear the nested place form
- when user enter data in the nested place form, it will reinitiate
the place select

how can I manage the duplicated attribute param ? ( should the js
script add/remove the corresponding html elements ?)
I'm a little bit lost in translation.....