I have been here 4 years now and live in Happy Valley.
I can honestly say if it suited my children and schools I would love to live near Port Noarlunga, it's a wonderful seasidey area, to have the sea so accessible would be wonderful, I am only 10 mins away at the moment. My other choice would be Brighton , but can't afford that lol. Port Noarlunga in my opinion is not "cheap".
My husband works north of the city and I have no desire to move there. What you have to remember is 5 years ago the exchange rate was fantastic for every say £100000 you had it gave you $250000,now you will be lucky to get $150000. That's a big difference.
Take time to have a look around and make your own opinion, you will get a feel for the right area. I have no desire to go north of the city as everything I want and need is here in the south.