Have driven through Baker on the way to GBNP and neither the town nor the RV "parks" are inspiring. One of those places kind of on the edge of civilization. As noted, depending on when you are going, the elevation in the park is pretty high so AC may not be needed. (Upper Lehman is around 7600'.) You might also consider staying in Ely if you need hookups.
Ken & Allison
2 Camping Cats (1 diabetic)
1996 4Runner, TRD Supercharger, Edelbrock headers
2007 Fleetwood Arcadia, Honda EU2000i
4 mountain bikes, 1 canoe, 4 tents, 8 sleeping bags, 2 backpacks
(You get the idea!)