I'd like to start an organic vegetable garden but am renting so I need to be able to get rid of it when I leave here (could be in 6 months to a year). One thought has been to plant in pots so I need to know what and when to plant in pots as I don't think I can dig up their backyard (even though it's a mess of weedy grass).

Also can I plant pumpkins on a grassy sloping hill? I guess pumpkins wont require much soil preparation but that's only a guess.

I live in a coolish climate (on a mountain), in Tasmania Australia so it's Summer right now. Sunny almost every day but also windy and quite a lot of rain.

If anyone can help I would really appreciate it. Even if I can just grow a few things in some pots I would be happy but I am an amatuer.
Are the grow bags 'organic' veggie friendly?
There are some really helpful answers and I don't know who to pick! Thank you 🙂

I agree – see if they'll let you do up the garden.
But if they won't, I recommend using growbags.
We're in a rented place and the garden is all concreted over so we don't even have the choice to ask. But we grew loads of courgettes, tomatoes and cucumbers last year using growbags, dwarf beans and sugarsnap peas in pots, and lettuces and spring onions in windowboxes. It was our first time, but we got great results!
For pumpkins, I'd say plant them in a growbag and just let them spread down the hill. They are quite heavy feeders, but with a growbag the soil is already prepared for you, with all the nutrients they need!
If you want to grow potatoes, use a dustbin with holes and stones in the bottom for drainage. Plant three seed potatoes about halfway down, then as they grow cover the plants up with more and more soil until you reach the top (this makes the plant put out more and more roots, thus more and more potatoes!). To harvest, just tip the whole lot out!
It doesn't have to be as scientific and complex as the answerer above describes; just go somewhere that sells seeds, choose some varieties you fancy (for best results go for those that say they're pest resistant, disease resistant or highly productive), and plant them whenever it says on the pack.
Good luck!