Yep...if you're trying to get the best possible deal, May through September are good. Babies have been hatching for a couple months and breeders need to keep the workload from getting out of hand as they hatch more.
I don't know if I'd be looking to save a few dollars by buying a fresh baby. You can usually find just as good a deal (or close enough) on a well started 100+ gram snake. Breeders hatch most of their year's production between late spring and early fall, so it's not like they're going to sell out for the year before September or October. Just take your time and find a good deal on a nice looking, well started baby.