Yes, you can make ADR's for the Garden Grove just like any of the other WDW restaurants. I just made one last week for the Garden Grove for a Friday night meal w/Timon & Rafiki.
RUN AWAY!!!! RUN AWAY AND DON'T LOOK BACK!!!!!!!!!!!!!
Seriously - I had my worst dining experience EVER at Garden Grove last summer. Perhaps it is because we were later in the evening, but the place was just so stale. Only the characters made it even worth considering. I hope it goes better for you than it did for us.
Yes. Regular ADR process. Disney Dining takes ADR's for the S/D as well.
The Garden Grove is 'off the beaten track' being at the Swan, and doesn't get alot of attention, so ADR's may not be needed. Still, it can't hurt to have them.
We went for w/e breakfast last October. Had Chip & Dale, Goofy, and Pluto. Great character interaction, and the food was almost comparable to Fresh at the Dolphin. We'll definitely be going back for breakfast next trip.
Dinner menu seemed interesting, but overpriced.