I can't guarantee that this will work. But it is what I would try first.
<select name="recipients" >
<option selected value="email1_AtMangle_domain.com">Location1</option>
<option value="email2_AtMangle_domain.com">Location 2</option>
_AtMangle_ would of course be the At Mangle you setup for formmail.php to hide the recipients true email from Email Harvesters. If you didn't specify one (you should consider it ) just use @ instead. Hope it works!