[SalesForce] Can’t use selected picklist value to render a outputpanel

I have a dynamically generated picklist, which generates fine below:

> public string ConNames {get;set;} 
> List<SelectOption> options = new
> List<SelectOption>(); Public list<SelectOption> getAccCons(){
>     system.debug('>>> Generating contact list');
>     List<Contact> conList = New List<Contact>();
>     conList = [SELECT Id, Name FROM Contact WHERE AccountId = :AccId];
>     options.add(new SelectOption('--None--','--None--')); 
>     For (Contact con : ConList){
>         options.add(new SelectOption(con.Id,con.Name)); 
>         options.add(new SelectOption('Create New Contact','Create New Contact'));            
>     }
>     return options;}

Which is used in a VF page as below:

    <apex:selectList value="{!ConNames}" size="1" label="Select Contact">
        <apex:selectOptions value="{!AccCons}"/>
        <apex:actionSupport event="onchange" reRender="test"/>
    </apex:selectList> 

If the select value = 'Create New Contact' I wanted to rerender the outputpanel 'Test'. I'm currently trying to use:

rendered="{!ConNames = 'Create New Contact'}">

But this is always returning false as ConNames is always null, what am I missing? I can see the rerender is working.