Very few ppl sail around Lakes entrance area. I only saw 1 other windsurfer when i was there fore 18 months and that was at Marlo.
The estuary at Marlo might work but its gunna be a short run to the sandbar.
Eastern beach might be sailable but unlikely, the shore breaks are super heavy along the 40 mile beach once they start breaking.
I agree with sailquik, paynesville will give you options out at the point but bring booties because there are lots of mussels in the water, especially near shore.
There is an OK surf break called the Bluff at the end of Red Bluff Rd near by. Looks like it should work in a westerly but I've only ever surfed it