I took my first trip in the Model 3 from San Jose to Yosemite just last weekend. Planned route was through Groveland where we stopped for lunch (Iron Door Saloon) and charged for about an hour (good enough to get from ~40% to 100%). We then entered the park via CA120 and drove out of it in order to check into the Yosemite View Lodge in El Portal (right on Highway 140). Our plan was to drive into the park the next two days and take the YART buses around the valley, then hit the Supercharger in Gustine on the way home but that wasn't what happened. We drove back in (free pass on August 25th; National Park Service birthday), took in some sights, did a little hiking and ended up at the Ahwahnee where I found the Tesla charger open for use (and so was the Level 2 charger). I plugged in for about 1/2 an hour (added 22 miles range) while we walked around, then headed out for dinner and returned to the motel. The motel offered use of a 120V outlet in the parking lot but I didn't think I would need it. They do not have any other EV charging infrastructure on the property from what I was told. The next day we drove in, parked at the Ahwahnee and again found both chargers open. Plugged into the destination charger and started the hike to Mirror Lake (actually Mirror Meadow since there wasn't really any water to speak of in it). Got back 2 1/2 hours later and the car was at 100% again. Ended up leaving the park with about 280 miles range left and made it back home via 140 with 121 miles left (without stopping to charge).
I wasn't planning to use the Tesla destination charger at the Ahwahnee since I figured it would be in use, but it wasn't. Both times I drove in both chargers were free. Both times I left, I was the only one there using it. I saw enough Teslas in the park those two days to assume that it would be difficult to rely upon using that DC but I guess I lucked out.
I think staying in Groveland and driving in, around and out of the park would be quite doable with a P3D-. It's about 50 miles from Groveland to Yosemite Valley, downhill on the way in. We prefer to say in El Portal since it's only a couple of miles from the "west" (Arch Rock) entrance so it gives us a little more time to sleep in before starting our hikes.
edit: Forgot to mention... when I got to the SC in Groveland (about 12:45pm on a Sunday) there were three other Teslas already there. I picked 4A since I did not see 4B anywhere (there are 7 stations; which is odd in more ways than one). When I left, there was only one unused station.
