My first module - a dashboard - SQL performance question

I'm trying to create a dashboard module with the Jquery UI. It's based on the iGoogle dashboard.

And I'm very near in finishing the base of it.

Just a bit of info about the module:

• As admin you can choose what blocks you make available for the dashboard + give a info about the block.
• Every user can then add the blocks he wants on his dashboard (with an ajax-call)
• there are 3 columns on the dashboard
• Blocks on the dashboard can be dragged around (position is autosaved with ajax) or deleted (ajax call)
• The content of the blocks can be hidden (also autsaved with ajax)

Now the question.

The position of the blocks on the dashboard is saved in a sql table. I'm curently saving the blocks in a string per column.
Something like this.

Col_0: (3v1, 5v1, 9v0)
Col_1: (1v1, 6v0, 10v1)
Col_2: (2v0, 8v1)
user: 1

where a block value is %v% (the first % is the block id and the second % is for the visibility)

So it's one row/user.

Is this the way to go (perfomance wise), or should I use one row per block with the column, the user and the visibility in it (wich creates a whole lot of rows)?