Are there any tools to go from ERD to DB design and vice versa?
Since you're using MySQL, you might want to take a look at MySQL Workbench.

It might not quite display the ERDs you're expecting but it gets the job done.

And it does have an import feature. I have only used it to import SQL files but apparently you can import from existing MySQL databases.



Also, a long time ago I found the following tools; but were not quite useful to me back then (perhaps they've matured by now):


Database Design Tool - DDT
Mogwai ERDesigner