it all depends on wich way the hill slopes. get a compass or google earth'it and see if it is a south sloping hill. ie... when your standing on the hill looking down towards the bottom where the stream is, are you N,S,E or West. if you are facing south it sounds like it could be a good spot. if your facing north it's probably no good at all! if your east or west it should do but, you might only receive a half-day of direct sun exposure. this is for the northern hemisphere where im located, i think it's the other way around for the southern hemisphere idk for sure though.
considering you ARE on a southern hill, where (?) to plant them depends on a number of things. the FIRST being, NOT on the side of the stream bank or in flat/level ground next to the stream before the hill starts to rise. people often like to hike/canoe/etc.. down streams and, are more likely to find them in this area. also IF the stream floods and your plants are on level/flat land next to the stream, your plants could drown! also fog and moisture will possibly linger at the bottom of the hill near the stream and potentially rot your buds near harvest! all of that of course depends on your knowledge of this area!
the SECOND least desireable place is on top of the hill because, you/plants will be much more easily detected by aviation/choppers. on top of that your plot will dry out faster wich, will make you hike up and down the whole hill with jugs of water for 6 months!
so i would go with somewhere towards the middle give or take! try to find some thick vegetation that people wouldnt ever want to go in, then cut out small patches here and there and put a plant or two. look into inclinometer/clinometers and a degree's of sun elevation for your area. if the whole hillside is heavily wooded with tall trees, even if south facing, your probably out of luck though.
im wasted, happy new year! and good luck!