The bus and train stations in Galway are approximately 1km from the University, and it should take 10-15 minutes to get there on foot.
A quick Google for hostels throws up lots of results in Galway City Centre – there should be no need for trekking to somewhere kilometres away. Expect to pay from €20 for a bed in a dorm – but do book as soon as you know you’re coming to the conference, as Galway is a tourist destination at the weekend – even outside the summer!
Another option may be trying a B&B in the area – they do reasonable rates too, and there’s lots of modern and stylish options in town. If you want a cracking view, you can travel a little further to Salthill, it’s absolutely beautiful, but still within walking distance of NUI Galway.