We stayed at Furnace Creek in February last year. It was fine--nicer than the overflow parking lot across the road. An advantage was a mere $5 fee to use the resort swimming pool. We also stayed near the park at the Shoshone (CA) RV park. This was a nice little low-key place, nothing fancy, across the road from a nature preserve and with a warm springs swimming pool. Shoshone RV Park - Shoshone, California
At this time of year, we would probably head for the highest campground in the park to avoid the heat!
Gas in the park is very expensive, and distances between gas stations are huge. Just something to keep in mind.