Hi Saxa
I had cause to be at Ag.Geor. last week so all I can tell you is that, like Arillas, there is much preparing/sprucing up going on . The vast beach is looking good and taking shape very nicely. Not sure where Villa Katerina is though.
With regards to pool usage, I would think that, like all other resorts, you would be allowed to use any pool. Just look for the sign outside which says "Free Pool"
Of course it's not "free" as you know and it's always good to buy a drink or two so you can make use of their sunbeds .
Not sure about July "Nightlife" but would imagine, with a resort of this size, there would be something always going on somewhere.
Cheers
Negg