How can i access MySQL of a local Acquia Dev website using the command line?
The easiest way to access a CLI database on any site is with drush:

~$ drush help sql-cli
Open a SQL command-line interface using Drupal's credentials.

Examples:
 drush sql-cli                             Open a SQL command-line interface 
                                           using Drupal's credentials.       
 drush sql-cli --extra=-A                  Open a SQL CLI and skip reading   
                                           table information.

Options:
 --database=&lt;key&gt;                          The DB connection key if using  
                                           multiple connections in         
                                           settings.php.                   
 --db-url=&lt;mysql://root:pass@127.0.0.1/db  A Drupal 6 style database URL.  
 &gt;                                                                         
 --extra=&lt;--skip-column-names&gt;             Add custom options to the mysql 
                                           command.


If you don't give it any options, then it will use the normal drush magic to find the settings for the current site you are in or from the site alias that you are using.

$ cd /path/to/your/drupal/docroot
$ drush sql-cli


TL;DR, if you can drush to your site, you can instantly connect to it with drush sql-cli