I have been scheduled for a c-section because my previous 2 births ended up being emergency sections, and the docs said the scar would be weak and I would risk rupturing during labour, putting both mine and baby's lives at risk. However, I have heard of a number of people having vaginal births after one or two sections, so it is definitely possible. If I had argued for it, they would have let me labour under close monitoring, but that would mean lying on my back the whole time, which is not the best position for anyone in labour. Also, I feel a section is safest for me and baby as my younger son had a heart defect and there is a slight possibility this baby might have some difficulties, although everything has been fine so far. I think I am far too well informed about what can go wrong during labour, but c-sections are no walk in the park either! If I had just had one previous section with no complications with baby, I would definitely be going for a natural birth. It's got to be worth a try, and if you're in hospital anyway they'll be able to act quickly if things aren't going to plan.
Hope everything goes well for you no matter what you decide!