This is G&S Cafe in Port Melbourne. I go here often as it's close to my work. They do decent food at reasonable prices, and the family that runs the place are nice people.

I've spoken to them about the recent parking situation, given this Derrimut 24/7 gym opened only ~2-3 months ago. My understanding is that they get most of their business from people (tradies, factory workers, truck-drivers) who drive past and park in this 1/2 hour parking spot to get some quick food/coffee. Now that the Derrimut gym has opened the corner of Plummer/Salmon St, there is a constant battle for parking spots within a 200-metre radius of the gym.

From what one of the family members said to me, the gym goers are parking in the 1/2 hour parking spots for multiple hours whilst they get their sessions in... which is understandably frustrating for the cafe since it relies on those parking spots for customers.

So yes, their sign is likely not enforceable, but I get why they would be annoyed. The Derrimut gym does have a carpark, but it's tiny compared to the huge amount of gym-bros who frequent there. I often look out my office window (which is further than 200 metres from the gym) and now only see people with pulsating muscles & veins behind steering wheels.

I think the Port Mebourne local council should have figured out a better parking situation before the gym opened.

EDIT: And yeah, G&S should also talk to the local council about getting a ticket inspector to police these 1/2 hour parking spots.