I was just there in May and, due to snow over the last patch of road, had to hike about one mile up to the grove. It was worth it though as No One else was around, especially at dawn the next day, and the area is beautiful. By now, snow won't be an issue.
I don't have any coordinates, but THE Patriarch Tree in the Patriarch Grove is approx. 100-200 feet from the parking lot at the top, has a sign and is very easy to see due to it's size. You won't have any trouble finding it.
If you plan to see the ancients in the Schulman Grove, be prepared for a 4-mile loop hike and in any event, take more water than you think you'll need. The combination of all the elements at those elevations (approx. 11,000 & 10,000 feet respectively) makes for a very desiccating environment.
I hope this is helpful. It's an awesome location and the trees are amazing and beautiful photographic subjects.
Phil