Just off the top of my head, and I've tried a few hoyas over the years. Overall, the rule with hoyas is they love to be potbound! In the ground that's difficult to achieve. Having said that though, I've planted H. carnosa - the pink 'wax' flower, the hardiest of them, and they've grown ok, though not rampantly by any means; really, they didn't thrive. Also, remember never to cut off the flowering stems as they flower from those points every season. To be quite honest, if I were you, I'd consider something else for growing in the ground on lattice.

Most are epyphites and the (initial) roots need a well-draining mix. The danger with planting in ground is that you may not achieve the right drainage and they could rot. Or be swamped by other plants. I've seen some growing OK (not flowering very well though) in a raised garden bed in a local park, growing up a metal trellis. Once established, they will happily climb other things and use the additional roots they make, to cling for support and can attain food thru those as well as the leaves. So you could do that and mist them occasionally with a foliar feeder, but I would be inclined to put the plant in a pot above the ground, even disguised with a bit of wood or rocks, to ensure it doesn't drown. Also check light conditions as they will grow OK almost anywhere but flower better with better light.

Kerris1 - I have seen many hoyas growing in the ground - in tropical and subtropical rainforests. In fact - I can point out several spots in the national park neighbouring my home where Hoya australis grows absolutely rampant over rocks and cliff faces out of the ground. Some hoyas even need to be planted where they can climb to great heights before they will flower (eg. Hoya lauterbachii), and it is very common to see Hoyas such as potsii and australis. rupicola growing over trees and rocky cliffs in parts of the tablelands west of Cairns.

The main thing all these ground growing hoyas have in common is very shallow, very well drained soil - sort of like growing bonsai, and for some of them (rupicola in FNQ and australis in Brisbane) very distinct dry seasons.

You have not told us where abouts in oz you are from - regardless - I think you will have the best chance of ground growing hoyas if you plant native ones, and even then it is probably dependent on the climate and what part of the country you are planting them in... I doubt any would thrive in colder parts of the country regardless of their species.