Do you have mobile devices yourself? If so, then contact a few studios that are in your area and ask for a portfolio of the sites they've designed for mobile devices. Test each link on your mobile devices and see how they perform. You want to see if they format appropriately for the medium - say a Samsung Nexus sees the site with larger buttons & links, the advertisements realign to a prominent place on the page, video & Images are sized nicely not just scaled. You want to make sure that 'Desktop Version' is available and works as you expect.
If possible it is better to find something locally as you can meet face to face and really get a sense if you trust the studio or not.