Hi Luka, I think that one is still up for debate - within an hour you have a lot of darker coastal regions but then... its still on the coast
Heading East you run into dark skies pretty fast but you're surrounded by high trees most of the time. From freo, somewhere south-east may be a good option but I'm not familiar with what's out that way.
Hopefully a few of us will get together soon and head to a dark site for a night or two and if so we'll let you know - I'm tied up on the weekend you suggested unfortunately.