"... Is my only option is to create a parallel web page with no MLS so I can have the right keywords in the URL?"
Yes, I wold think making a new page with keywords in url would be the best way to go.Once PR and link equity has been established you can always at that time 301 redirect to the wordpress mls query page.
But if you have to optimize the wordpress site page with MLS query, not having keywords in the url is not the end of the world. You can sstill do alot to optimize that page as is with good content, quality links and a social media blitz.