You can use Synaptic to setup the fastest server for updates:

1. Launch Synaptic from the MintMenu (i.e. search for "synaptic" and run it).

2. From the Synaptic menu select Settings -> Repositories.

3. Select the Software tab in the Download From drop down, choose Other…

4. Click the Select Best Server button in the resulting dialog and wait a minute or perhaps more on a slow connection.

5. Once it’s finished select your server and click on Choose Server. close everything and click Reload in the main Synaptic window.

6. Close everything and click Reload in the main Synaptic window.

7. You should see Synaptic downloading package information in progress from your new mirror.

This simple procedure picks the best mirror for you.

Source, with screenshots: How To select fastest mirror in Ubuntu