You would need to send the options formatted for HTTP POST, you can't just pass an array through like that.
Something like this would work.
/* poll variables below */
,'poll_title' => 'Cast your vote'
// poll_options: Array of objects with keys 'title' (string), 'answers' (array of objects with key 'value' set to the choice) and 'multichoice' (bool)
,'poll_options[1][title]' => urlencode('Make your choice, either Yes or No:')
,'poll_options[1][answers][0][value]' => 'Yes'
,'poll_options[1][answers][1][value]' => 'No'
,'poll_options[1][multichoice]' => '0'
,'poll_public' => '0' // bool Make the poll public
,'poll_only' => '0' // bool Make this a poll-only topic
You also don't need to urlencode everything like that, cURL sends data as application/x-www-form-urlencoded by default.