The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Others can advise you about access and conditions much better than I can. I understand that the Little J does have March Browns. They should be emerging now. As is the case on many Eastern waters, that hatch is often sparse rather than concentrated and often extends into early June. The "sulphur" that should also be emerging is invaria. On most PA trout streams that have them, the dorothea hatch typically begins later (toward the end of the month). Although I'm not at all sure that "true" dorothea occur on the J, perhaps there are some. Many of the smaller, later sulphurs that are often attributed to dorothea are continuations of the invaria hatch. In areas with extended hatches of invaria, they become smaller and somewhat lighter in color as the hatch continues. However, that taxonomic distinction makes only very slight differences from a fishing standpoint, and probably is only of interest to nitpickers (like me). :)