Bring your computer, pull up a chair and code to your heart's content. If you get stuck, you're surrounded by other Rubyists and can ask them a question.
This event is a great opportunity for beginners to work through tutorials (with mentors nearby to help if you get stuck), to pair with other developers of all skill levels, or just focus on some code you've been meaning to get to for the last month.
There will be water, tea and coffee available but will not have any other drinks. Please also let us know about dietary requirements or other options for you so we can do the catering.