I think the only time you don't want to prune is in the late fall when pruning could stimulate new growth right before dormant season. I prune right before spring and then continually prune all summer to take off new growth I don't want

I'm no expert, so take my advice with a grain of salt

Dandy:

I'd second the advice you've gotten. Apricot is different timing due to disease issues.

I'd also second jimmy's advice about summer pruning. I prune all summer as needed to control height and vigor.

1) Not being an expert, my understanding is that now is the appropriate time to prune (at least that's what I gathered from the Dave Wilson Fruit Tube videos). I just did some work on a plum tree.

2) I'll take some of your lower chill peach/plum cuttings! I just posted over on the plant exchange forum.

Here is a link that might be useful: WANTED: low chill peach, nectarine, apricot, or plum scions

Pruning in late Summer helps avoid bacterial canker.

Here is a link that might be useful: Summer pruning

I've always felt that if it's dormant, it's prunable. I did about half the orchard in December, and the other half in January. I've also come to the decision, after ignoring trees all summer and then seeing all the wild growth that needed pruning, that some attentive summer pruning is in order. Planning on trying to stay on that this year. Especially for the peaces and plums!