On the table on pages 46-47 under the Speak Language skill, it does not list "Gnome" under language. But on page 212, for the Zilargo region, it lists "Gnome" under languages spoken.
It's worth noting that the Gnomes (as one of the four natives races) have been on Khorvaire since before humans migrated over from Sarlonna ... so it's a fair bet they weren't mute before the Common tongue.
(The other three are halflings, orcs and goblinoids)