Fly into Santiago and then make an audable.
This is the best advice. Termas de Chillan likely would have the best overall track record for early season snow in South America. That would be 5 hours by train/car south from Santiago. If Portillo or Valle Nevado group look better when you arrive, those will be easy options much closer. You could also get a bus from Santiago over to Mendoza, then 240 miles south from there to Las Lenas. Forget about Bariloche: harder to get there, snow is unreliable even mid-season, so it would take a miracle for it to be any good in early July.
As I've said numerous times snowfall down there is very erratic. If you have to go in early July vs. August, buy the airfare now but NOTHING ELSE until you know for certain where the snow is.