They will probably always have buds on, there's a difference between having buds, and buds which are actively growing (when they just start growing it's called 'bud burst' which I quite like the sound of). I would prune even if they are growing, preaches can take quite a hard prune, one of my books suggests that you can take up to 75% of previous years growth off. They fruit off previous years growth through, so make sure you don't take it all off!
There seems to be a growing trend to actually do summer pruning with stone fruit instead of winter pruning, I haven't gone into it much myself, the main theory I think being that the tree will heal the wounds quicker when it is actively growing.
Firstly I should say I'm a total novice at this... but I have also been told that summer pruning helps avoid the tree getting rot in the pruned branches. In winter this is harder to do due to lack of growth and the general dampness which encourages funghi. It sounds like fair advice to me and ties in with what Christy says. But as I said, I'm no expert by a long shot so you should check up on that. I have a peach too but so far, I think I'll wait until after fruiting to prune. I would love to hear if you discover any other tips regarding peach trees in particular.
The other advantage to pruning your stone fruit in summer If you have a few varieties of fruit i have discovered is that it lightens the winter pruning work load. I have not long finished a marathon of apples, gooseberries, red currants, various brambles and far too many roses, and have been thanking my lucky stars I did the plums, peaches, peacherines, nectarines and apricots in summer as recommended by an organic gardening book, easier to get a spell of fine weather to prune in as well in the summer.
Hi Caroline, we just pruned a whole lot of Peach trees here in Gizzy and some of them had already started to bud...i guess we get mild weather here so perhaps its not so much of an issue however you should only ever take a third of the tree off at a time : )>.