The best thing for your dahlia cuttings is to find a nice sunny place in the garden with rich moist soil and gently set them in. Try to lift up the entire root ball with the potting soil intact and set it into the planting hole. Consider shattering the pots (if terracotta) with a hammer as not to disturb the roots which will greatly reduce planting transplant shock. I've tried growing dahlias in pot and wasn't the greatest idea. They are very thirsty. Unless you use a very large pot, it could work. They need constant watering and the roots need plenty of space to expand and create the tubers. You'll need to bring them indoors after the first frost.

Don't plant them out in the autumn - that's when you lift them and bring the corms under cover out of the frost for the winter. Plant out? Depends how big they are. They are a magnet for slugs and snails. As they will possibly be too young to flower very prolifically this year I would pot them on rather than planting out and reduce the risk of them being eaten. You can always put copper bands round the pots to deter them. Don't leave them in small pots and let them get root bound anyway.
If you have good soil and few slugs you could risk it - why not do half and half?

Thankyou both.