Adelaide is a fabulous city: people, food, sunshine, and cafés. However, the 120 plus wineries that lie within a 45-minute drive of the centre of the city, are a standout. Many have a serious international reputation, good cellar door prices and free tastings.
There are three regions making wine directly on the edge of the city's suburbs. The Barrossa Valley in the north, MacLaren Vale in the south, and the Adelaide Hills in the east. On the west is St Vincent Gulf which is too wet and too salty (and too deep) to grow vines.
To taste effectively you need a wine taster's map of the region you are choosing to visit. Allowing two days per district is well in order. The trouble is not in finding the wineries themselves (sign posting is universally excellent), nor is getting to them (the wine districts are on the main south, north and eastern routes out of the city - namely Main South Rd, Main North Rd and the Great Eastern Freeway), but picking which ones to visit. Most are very good, many are excellent and a few are hilariously bad. While the bad ones can be good for a laugh if you have the time to enjoy them, it can be disappointing if you miss out on a gem because of them.
Find yourself a local. Despite Adelaide having Australia's premier brewery in the leafy inner eastern suburbs (Coopers), most people in the city have a more than passing interest in the local wines. The information you will get from someone at a café, church or even in the street may be passé or even wrong, but they'll probably have an opinion and not be afraid to tell you. Most bottle shops have a resident expert who will be able to take up large quantities of your precious time with advice, some of which will be good and up-to-date. There are heaps of mini-buses making day-tours and afternoon-tours if you don't want to make your own decisions.
Once you have made your choice of wineries (four in a day is safe) and have located your first winery's front door, go inside. Note that in McLaren Vale especially, a lot of wineries sell their wine from sheds (even some very good wineries still operate from corrugated iron sheds), so don't let that confuse you or put you off. Few wineries have artificial limits on how much you can taste: most will willingly let you try everything that they make. If you're driving though, keep to a maximum four wineries - it's a survival thing.
In the small wineries, the wine tasting areas are typically supervised by British Backpackers with tourist visas. The big ones have professional wine tasting supervisors. In some, the wine maker will spend some time in the wine tasting area (the last time this Researcher was at Simon Hackett's in McLaren Vale, Simon was reading the paper in the corner drinking coffee). Attitudes towards tasters who speak pretentious gibberish varies. Feel free, but never take the tasting experience too seriously. Wine is for drinking, tasting and making friends over. Most wineries will try and help you do all three things.
Finally, Jacob's Creek, the watercourse, does exist. It is singularly unexciting. It has water in it only in winter (and then only when it is raining). It is in the Barrossa Valley. This entry does not recommend going out of your way to find it, although you probably will cross it a couple of times as you drive around the Barrossa for long enough.