Mobile Menu – not converting to dropdown

Hello, I have read some of the threads people have listed here that say Twenty-Eleven is, in fact, a responsive theme. However it’s not displaying my main menu the way I would expect, and the way that other truly mobile-responsive themes do, converting all of the main menu items into a dropdown list, under the heading “Menu”.

Instead, I see the full nav bar of all my main menu items, wrapping my iPhone screen width three times.

I’m still in development, so here’s the current site: https://69.195.124.167/~eastbbc2/
It looks great on a large screen, but pretty crappy on a small one as the menu items wrap and stack on top of each other.

How can I make the main menu appear as a drop down for smaller screens? This seems a default on truly responsive themes. Thanks!

PS – if there’s a better theme I should be using, please advise. Lots of our end users will be accessing the site from mobile so it’s a big priority.