Yes. Only admin are able to change the font of their community by following the steps below:
Admin Panel> Theme> General> Font Family> Save.
To make sure the same font getting displayed on the mobile devices, you need to include the proper <link> tag in the Theme> Advanced Settings tab if needed.
e.g. <link href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,60029" rel="stylesheet">