Im Glad you asked, the easiest way is by car (or someone else’s car) But there are buses that do run up to Gumeracha at least a couple of times per day on Saturday only, they all leave from Tea Tree Plaza Interchange in Modbury
Link Sa have services running from Tea Tree Plaza to Mt Pleasant on Sat, which will stop at the oval in Gumeracha (where the fair is),
For timetables and more information please check out: www.linksa.com.au
Gumeracha is the small country Town with the Giant Rocking horse about 45 mins from North Terrace and 20 mins from Tea Tree Plaza in good traffic conditions. Continuing up North East Road and following it all the way into Torrens Valley Rd is the easiest way of getting there.The fairground itself is in Federation Park which is the large scenic park connected to the Town Hall and Football oval, just around the bend as you enter the town, you cant miss it! Signs will also be up around the area to let you know you are on track.
If you are visiting to enjoy the fair, the best spot to park would be on the oval, the entrance is just past the town hall, gate 3. It is likely the Football Club will still be charging $5 per car for all day parking.