I know that nectarines fruit on one year old growth from the previous year, so pruning them might be sacrificing that season's crop. If you're attempting to train the fruit trees into an Espalier pattern, expect to sacrifice at least a portion of the fruit crop while you prune a tie off the branches into the pattern you want. Worry about the fruit later in that case. If you want fruit sooner than later, don't prune them. Or, you can do the old orchard farmer's trick of pruning HALF of the tree one year and then pruning the other half the next year so you'll still get a partial crop.